AU2017245346B2

AU2017245346B2 - Image forming apparatus

Info

Publication number: AU2017245346B2
Application number: AU2017245346A
Authority: AU
Inventors: Takuma Ishihara; Yukari Motosugi; Akira Sakamoto; Takeshi Zengo
Original assignee: Fujifilm Business Innovation Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 2016-10-17
Filing date: 2017-10-11
Publication date: 2018-08-16
Anticipated expiration: 2037-10-11
Also published as: JP2018065262A; JP6852346B2; CN107953669A; AU2017245346A1; CN107953669B

Abstract

Abstract An image forming apparatus includes plural ink droplet ejection heads of respective colors, the ink droplet ejection heads being arranged in a transporting direction of a recording medium and ejecting inks of different colors toward the recording medium; an infrared radiation device that is disposed between the ink droplet ejection heads of the respective colors and that radiates infrared light toward ink droplets on the recording medium; and a drying device that is disposed downstream of one of the ink droplet ejection heads of the respective colors that is most downstream in the transporting direction of the recording medium, the drying device drying the recording medium by heating the recording medium. C,4 o4 coN (c9

Description

DESCRIPTION

Background (i) Technical Field

The present invention relates to an image forming apparatus .

(ii) Related Art

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Japanese Unexamined Patent Application Publication No. 2011-110922 discloses a printing system which includes heads for ejecting electromagnetic wave curing inks of respective colors toward a medium and in which the inks on the medium are cured by radiating electromagnetic waves that correspond to each head. In this printing system, the radiation conditions of the electromagnetic waves are adjusted on the basis of the amounts of inks that are ejected.

Japanese Unexamined Patent Application Publication No. 2013-188920 discloses an inkjet recording apparatus which includes heads for ejecting inks of respective colors toward a medium and in which the medium is dried by radiating an infrared laser for each head. In this apparatus, the concentrations of infrared absorbents contained in the inks

2017245346 11 Jul 2018 and the intensities of the infrared lasers are adjusted in accordance with the ejection order so that the medium is heated to the same temperature for each head.

When the inks that have been ejected toward the medium are dried by using only the infrared lasers, the temperature needs to be maintained lower than or equal to 100°C for a certain period of time until the inks dry, so that the inks are not boiled and spattered. Therefore, plural infrared lasers may need to be arranged in a transporting direction of the medium and subjected to temperature control individually.

Summary

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

An embodiment of the present invention provides an image forming apparatus having a structure simper than a structure in which drying is performed only by infrared radiation devices that are each disposed downstream of a corresponding one of ink droplet ejection heads of respective colors.

An image forming apparatus according to a first aspect of the present invention includes plural ink droplet ejection heads of respective colors, the ink droplet ejection heads being arranged in a transporting direction of a recording medium and ejecting inks of different colors toward the recording medium; an infrared radiation device that is disposed between the ink droplet ejection heads of the

2017245346 11 Jul 2018 respective colors and that radiates infrared light toward ink droplets on the recording medium; and a drying device that is disposed downstream of one of the ink droplet ejection heads of the respective colors that is most downstream in the transporting direction of the recording medium, the drying device drying the recording medium by heating the recording medium.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, one or more of the ink droplet ejection heads other than the most downstream ink droplet ejection head each eject ink containing an infrared absorbing material or black ink.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the most downstream ink droplet ejection head ejects ink containing no infrared absorbing material.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the ink containing no infrared absorbing material is light-colored ink.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, one of the ink droplet ejection heads that ejects black ink is not the most downstream ink droplet ejection head. When a monochrome image is formed by using the black ink ejected from the ink droplet ejection head that ejects the black ink, either the infrared radiation device or

2017245346 11 Jul 2018 the drying device is selectively operated.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, two or more ink droplet ejection heads that eject ink containing an infrared absorbing material are disposed downstream of the ink droplet ejection head that ejects the black ink. When the monochrome image is formed by using the black ink ejected from the ink droplet ejection head that ejects the black ink, the number of infrared radiation devices to be operated and a position of each infrared radiation device to be operated are selectable .

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the inks of different colors ejected from the ink droplet ejection heads of the respective colors are aqueous inks .

According to the first aspect of the present invention, the structure of the apparatus is simpler than a structure in which drying is performed only by infrared radiation devices that are each disposed downstream of a corresponding one of ink droplet ejection heads of respective colors.

According to the second aspect of the present invention, the recording medium onto which the inks have been ejected by the ink droplet ejection heads of the respective colors can be pre-dried by the infrared radiation devices disposed downstream of the ink droplet ejection heads of the respective colors .

2017245346 11 Jul 2018

According to the third aspect of the present invention, color turbidity of the ink ejected by the most downstream ink droplet ejection head is lower than that in the case where the most downstream ink droplet ejection head ejects ink containing an infrared absorbing material.

According to the fourth aspect of the present invention, color turbidity of the light-colored ink is lower than that in the case where the ink containing an infrared absorbing material is the light-colored ink.

According to the fifth aspect of the present invention, unlike the case where the selective operation of either the infrared radiation device or the drying device is not performed when the monochrome image is formed, the recording medium onto which the black ink has been ejected can be dried by the infrared radiation device or the drying device as appropriate .

According to the sixth aspect of the present invention, unlike the case where only one ink droplet ejection head that ejects ink containing an infrared absorbing material is disposed downstream of the ink droplet ejection head that ejects the black ink, an appropriate drying mode for drying the recording medium onto which the black ink has been ejected can be selected.

According to the seventh aspect of the present invention, the ink droplet ejection heads of the respective colors are capable of ejecting the aqueous inks more easily than in the case where the inks ejected by the ink droplet ejection heads

2017245346 11 Jul 2018 of the respective colors are oil-based inks.

According to a further aspect of the present invention, there is provided an image forming apparatus comprising:

a plurality of ink droplet ejection heads of respective colors, the ink droplet ejection heads being arranged in a transporting direction of a recording medium and ejecting inks of different colors toward the recording medium;

an infrared radiation device that is disposed between the ink droplet ejection heads of the respective colors and that radiates infrared light toward ink droplets on the recording medium; and a drying device that is disposed downstream of one of the ink droplet ejection heads of the respective colors that is most downstream in the transporting direction of the recording medium, the drying device drying the recording medium by heating the recording medium; and a control device that selectively controls the operation of the infrared radiation device to evaporate 30% to 50% of moisture in the ink droplets.

Brief Description of the Drawings

An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:

Fig. 1 is a schematic side view of an image forming apparatus according to an exemplary embodiment;

Fig. 2 is a schematic side view illustrating the manner in which a monochrome image is formed by an inkjet recording

2017245346 11 Jul 2018 head for black ink in the image forming apparatus illustrated in Fig. 1; and

Fig. 3 is a graph showing the temperature reached by continuous paper and the amount of moisture remaining in the continuous paper relative to the intensity of an infrared laser radiated toward the continuous paper by an infrared radiation device.

Detailed Description

An image forming apparatus according to an exemplary embodiment of the present invention will be described with reference to the drawings. In the drawings, the direction indicated by arrow UP is defined as the vertically upward direction of the image forming apparatus. In the following description, the direction in which a recording medium is transported may be referred to simply as transporting direction, and the upstream side and the downstream side in the transporting direction may be referred to simply as upstream side and downstream side, respectively. In this specification, any numerical range expressed by using the word to includes the values before and after the word to as the lower and upper limits thereof.

Overall Structure of Image Forming Apparatus

Fig. 1 is a side view of an image forming apparatus 10 according to the exemplary embodiment. As illustrated in Fig. 1, the image forming apparatus 10 is an inkjet recording apparatus that forms an image on a recording medium by

2017245346 11 Jul 2018 ejecting ink droplets.

The image forming apparatus 10 includes a paper feed roller 20 and a take-up roller 22. The paper feed roller 20 feeds continuous paper P, which is an example of a recording medium, at the most upstream position in the transporting direction of the continuous paper P. The continuous paper P is wound around the take-up roller 22 at the most downstream position in the transporting direction of the continuous paper

P. The continuous paper P is transported in the direction of arrow A by the paper feed roller 20, the take-up roller 22, and plural transport rollers 24, which will be described below The image forming apparatus 10 includes plural inkjet recording heads 12 (hereinafter referred to simply as recording heads) of respective colors as examples of ink droplet ejection heads that eject ink droplets toward the continuous paper P. The image forming apparatus 10 also includes infrared radiation devices 14, which are disposed between the recording heads 12 of the respective colors and which radiate infrared light toward the continuous paper P, and a drying device 16, which is disposed downstream of the most downstream recording head 12. The image forming apparatus 10 also includes a control device 18 that controls the operations of the infrared radiation devices 14 and the drying device 16. The transport rollers 24 are disposed between the paper feed roller 20 and the take-up roller 22.

The transport rollers 24 are in contact with the continuous paper P at a side opposite to the side onto which the ink

- 8 2017245346 11 Jul 2018 droplets are ejected, and transport the continuous paper P.

The transport rollers 24 are shifted upward (in a direction toward the recording heads 12) relative to the paper feed roller 20 and the take-up roller 22 so that a tension is applied to the continuous paper P.

The continuous paper P is elongated and is wound around the paper feed roller 20. The continuous paper P is pulled from the paper feed roller 20 and is transported in the direction of arrow A as the transport rollers 24 rotate. The continuous paper P transported by the transport rollers 24 is finally wound around the take-up roller 22 as the take-up roller 22 rotates.

In the present exemplary embodiment, the recording heads 12 include recording heads 12K, 12C, 12M, and 12Y which respectively eject black (K), cyan (C), magenta (M), and yellow (Y) ink droplets. In the present exemplary embodiment, the recording heads 12K, 12C, 12M, and 12Y are arranged with spaces therebetween in that order from the upstream side to the downstream side in the transporting direction of the continuous paper P. The recording heads 12K, 12C, 12M, and 12Y are arranged so that the longitudinal direction thereof coincides with the width direction of the continuous paper P, and have a length greater than or equal to the width of the continuous paper P. Each of the recording heads 12K, 12C, 12M, and 12Y ejects ink droplets of the corresponding color from plural nozzles thereof to form an image of the corresponding color on the continuous paper P. The recording heads 12K, 12C,

- 9 2017245346 11 Jul 2018

12M, and 12Y are generically referred to as recording heads 12 when it is not necessary to distinguish between the colors

K, C, M, and Y.

The image forming apparatus 10 includes four containers (not shown) that contain inks of respective colors for the recording heads 12K, 12C, 12M, and 12Y. The four containers are configured to supply the inks contained therein to the recording heads 12K, 12C, 12M, and 12Y of the corresponding colors .

The infrared radiation devices 14 are disposed between the four recording heads 12K, 12C, 12M, and 12Y of the respective colors, and include three infrared radiation devices 14A, 14B, and 14C in the present exemplary embodiment. More specifically, the infrared radiation devices 14 include the infrared radiation device 14A, which is disposed between the recording head 12K and the recording head 12C; the infrared radiation device 14B, which is disposed between the recording head 12C and the recording head 12M; and the infrared radiation device 14C, which is disposed between the recording head 12M and the recording head 12Y. Thus, the

recording	head	12K,	the	infrared	radiation	device	14A,	the
recording	head	12C,	the	infrared	radiation	device	14B,	the
recording	head	12M,	the	infrared	radiation	device	14C,	the

recording head 12Y, and the drying device 16 are arranged in that order from the upstream side in the transporting direction of the continuous paper P so as to face the continuous paper P. The infrared radiation devices 14A, 14B,

2017245346 11 Jul 2018 and 14C are generically referred to as infrared radiation devices 14 when it is not necessary to distinguish between them.

Each of the infrared radiation devices 14A, 14B, and 14C includes plural laser elements (not shown), which radiate infrared light (infrared laser) toward the continuous paper P onto which the ink droplets have been ejected by the recording heads 12. Each of the infrared radiation devices 14A, 14B, and 14C functions as an auxiliary drying unit, and pre-dries the ink droplets that have been ejected onto the continuous paper P by one of the recording heads 12K, 12C, and 12M that is immediately in front thereof in the transporting direction of the continuous paper P. The control device 18 is electrically connected to the infrared radiation devices 14A, 14B, and 14C, and controls the energy and timing of the radiation by the infrared radiation devices 14A, 14B, and 14C.

Any infrared laser having an oscillation wavelength in the range of 780 nm to 1100 nm, for example, may be used as each of the infrared radiation devices 14A, 14B, and 14C.

Each of the infrared radiation devices 14A, 14B, and 14C may be, for example, an infrared laser such as a semiconductor laser, a solid-state laser, a gas laser, or a dye laser. Alternatively, a high-output LED provided with a focusing optical system may be used.

Among the recording heads 12 other than the most downstream recording head 12Y in the transporting direction of the continuous paper P, the recording heads 12C and 12M each

2017245346 11 Jul 2018 eject ink containing an infrared absorbent, which is an example of an infrared absorbing material. In other words, cyan ink and magenta ink ejected from the recording heads 12C and 12M, respectively, contain an infrared absorbent. In the present exemplary embodiment, each of the cyan ink and magenta ink is aqueous ink containing a coloring agent of the corresponding color, the infrared absorbent, and an aqueous solvent. Aqueous ink has a viscosity lower than that of oilbased ink, and droplets thereof can be easily ejected from the recording heads 12C and 12M.

In the present exemplary embodiment, the infrared absorbent contained in the ink of each color has a local maximum absorption wavelength that is equal or close to the oscillation wavelength of the infrared light (infrared laser) that is radiated first after the ink has been ejected. More specifically, the infrared absorbent contained in the cyan ink has a local maximum absorption wavelength that is equal or close to the oscillation wavelength of the infrared light (infrared laser) radiated from the infrared radiation device

14B disposed immediately behind the recording head 12C in the transporting direction of the continuous paper P. Accordingly, the infrared absorbent contained in the cyan ink that has been ejected onto the continuous paper P by the recording head 12C absorbs the infrared light (infrared laser) radiated by the infrared radiation device 14B. When the infrared absorbent absorbs the infrared light (infrared laser), moisture in the cyan ink that has been ejected onto the continuous paper P is

2017245346 11 Jul 2018 heated and at least partially evaporated, so that the continuous paper P is pre-dried.

In addition, the infrared absorbent contained in the magenta ink has a local maximum absorption wavelength that is equal or close to the oscillation wavelength of the infrared light (infrared laser) radiated from the infrared radiation device 14C disposed immediately behind the recording head 12M in the transporting direction of the continuous paper P. Accordingly, the infrared absorbent contained in the magenta ink that has been ejected onto the continuous paper P by the recording head 12M absorbs the infrared light (infrared laser) radiated by the infrared radiation device 14C. When the infrared absorbent absorbs the infrared light (infrared laser) , moisture in the magenta ink that has been ejected onto the continuous paper P is heated and at least partially evaporated, so that the continuous paper P is pre-dried.

The infrared absorbents contained in the cyan ink and magenta ink are selected from, for example, infrared absorbents described in Japanese Patent Application No. 2015142373.

The black ink ejected from the recording head 12K (sometimes referred to as black ink in this specification) contains no infrared absorbent. In other words, among the recording heads 12 other than the most downstream recording head 12Y in the transporting direction of the continuous paper P, the most upstream recording head 12K ejects black ink. In the present exemplary embodiment, two or more recording heads

2017245346 11 Jul 2018

12C and 12M that each eject ink containing an infrared absorbent are disposed downstream of the recording head 12K that ejects the black ink. The black ink absorbs infrared light (infrared laser). Therefore, the black ink that has been ejected onto the continuous paper P absorbs the infrared light (infrared laser) radiated by the infrared radiation devices 14A, 14B, and 14C. When the black ink absorbs the infrared light (infrared laser), moisture in the black ink that has been ejected onto the continuous paper P is heated and at least partially evaporated, so that the continuous paper P is pre-dried.

In the present exemplary embodiment, the black ink is aqueous ink containing a coloring agent of the corresponding color and an aqueous solvent.

In addition, among the recording heads 12, the most downstream recording head 12Y in the transporting direction of the continuous paper P ejects ink containing no infrared absorbing material. In other words, the yellow ink ejected from the most downstream recording head 12Y contains no infrared absorbent. The yellow ink, which contains no infrared absorbing material, is an example of light-colored ink. Light-colored ink is ink having a low colorant concentration whose absorbance spectrum has a local maximum intensity that is 1/2 to 1/10 of those of inks of other colors In the present exemplary embodiment, color turbidity of the yellow ink can be reduced because the yellow ink contains no infrared absorbent.

2017245346 11 Jul 2018

In the present exemplary embodiment, the yellow ink is aqueous ink containing a coloring agent of the corresponding color and an aqueous solvent.

The drying device 16 is disposed downstream of the most downstream recording head 12Y among the recording heads 12 in the transporting direction of the continuous paper P. The drying device 16 functions as a main drying device, and is configured to perform a drying process (main drying process) on the continuous paper P by heating and evaporating moisture in the ink droplets of all colors that have been ejected onto the continuous paper P in a superposed manner. In the present exemplary embodiment, the drying device 16 dries an image formed of the ink droplets on the continuous paper P without coming into contact with the image (side of the continuous paper P on which the image is formed). The drying device 16 employs a heating method that uses a drum, a heater, hot air, etc., instead of the method employed by, for example, the infrared radiation device 14 in which heating or curing is carried out only at a specific wavelength. The drying device 16 of the present exemplary embodiment includes, for example, a heat source, such as an infrared lamp, and dries the continuous paper P by heating and evaporating moisture in the ink droplets on the continuous paper P.

The drying device 16 may include, for example, a hot air heater, which blows hot air toward the ink droplets on the continuous paper P, instead of the heat source such as the infrared lamp, and dry the continuous paper P by evaporating

2017245346 11 Jul 2018 moisture in the ink droplets on the continuous paper P with the hot air. Alternatively, the drying device may include a heating drum, which comes into contact with the continuous paper P at a side opposite to the side at which the image is formed, instead of the infrared lamp or the hot air heater, and dry the continuous paper P by evaporating moisture in the ink droplets on the continuous paper P with the heating drum.

The control device 18 is electrically connected to the drying device 16, and controls the operation of the drying device 16. The control device 18 operates all of the infrared radiation devices 14A, 14B, and 14C and the drying device 16 when a color image is formed.

The control device 18 selectively operates either one or more of the infrared radiation devices 14 or the drying device 16 when a monochrome image is formed by using the black ink ejected from the recording head 12K. When the control device selects one or more of the infrared radiation devices 14, the control device 18 determines the number of infrared radiation devices 14 to be operated and the position of each infrared radiation device 14 to be operated. In other words, the control device 18 determines which of the infrared radiation devices 14A, 14B, and 14C is/are to be operated.

When, for example, one or more of the infrared radiation devices 14A, 14B, and 14C are operated, spreading of the ink that forms an image on the continuous paper P and deformation of the continuous paper P are smaller than those in the case where the drying device 16 is operated. In addition, the

2017245346 11 Jul 2018 density of the image can be increased. The control device 18 determines which of the infrared radiation devices 14A, 14B, and 14C is/are to be operated among the infrared radiation devices 14 based on, for example, the amount of black ink droplets ejected onto the continuous paper P and the image formation speed. The control device 18 selects the drying device 16 when, for example, the continuous paper P has infrared absorption characteristics or when the continuous paper P is subjected to pre-printing (printing before main printing). Thus, the control device 18 selects an appropriate drying mode in which one or more of the infrared radiation devices 14A, 14B, and 14C or the drying device 16 is operated in accordance with, for example, the type of the continuous paper P, the printing mode, such as pre-printing, the image characteristics, such as the amount of black ink droplets, and the image formation speed.

Operation and Effects

The operation and effects of the present exemplary embodiment will now be described.

As illustrated in Fig. 1, when the image forming apparatus 10 forms a color image, the recording head 12K ejects black ink droplets toward the continuous paper P pulled from the paper feed roller 20. Then, the infrared radiation device 14A, which is disposed immediately downstream of the recording head 12K, radiates infrared light (infrared laser) toward the continuous paper P onto which the black ink droplets have been ejected. Accordingly, moisture in the

2017245346 11 Jul 2018 black ink droplets that have been ejected onto the continuous paper P is heated and at least partially evaporated, so that the continuous paper P is pre-dried.

Subsequently, the recording head 12C ejects cyan ink droplets toward the continuous paper P. Then, the infrared radiation device 14B, which is disposed immediately downstream of the recording head 12C, radiates infrared light (infrared laser) toward the continuous paper P onto which the cyan ink droplets have been ejected. Accordingly, moisture in the cyan ink droplets that have been ejected onto the continuous paper P is heated and at least partially evaporated, so that the continuous paper P is pre-dried.

Subsequently, the recording head 12M ejects magenta ink droplets toward the continuous paper P. Then, the infrared radiation device 14C, which is disposed immediately downstream of the recording head 12M, radiates infrared light (infrared laser) toward the continuous paper P onto which the magenta ink droplets have been ejected. Accordingly, moisture in the magenta ink droplets that have been ejected onto the continuous paper P is heated and at least partially evaporated, so that the continuous paper P is pre-dried.

Then, the recording head 12Y ejects yellow ink droplets toward the continuous paper P. After that, the drying device 16, which is disposed immediately downstream of the recording head 12Y, dries the continuous paper P onto which the yellow ink droplets have been ejected. The drying device 16 includes, for example, a heat source, such as an infrared lamp, and

2017245346 11 Jul 2018 performs a main drying process on the continuous paper P by heating and evaporating moisture in all of the ink droplets (yellow ink droplets and ink droplets of other colors) on the continuous paper P.

After the ink droplets that form an image on the continuous paper P have been dried, the continuous paper P is wound around the take-up roller 22. Thus, the operation of forming an image on the continuous paper P is completed.

Next, a case in which a monochrome image is formed by using the recording head 12K will be described.

As illustrated in Fig. 2, when the image forming apparatus 10 forms a monochrome image, the recording head 12K ejects black ink droplets toward the continuous paper P pulled from the paper feed roller 20. The control device 18 selectively operates either one or more of the infrared radiation devices 14 or the drying device 16 to dry the continuous paper P onto which the black ink droplets have been ejected. When, for example, the control device 18 selects the drying device 16, the drying device 16, which is disposed downstream of the most downstream recording head 12Y, dries the continuous paper P onto which the black ink droplets have been ejected. The drying device 16 includes, for example, a heat source, such as an infrared lamp, and dries the continuous paper P by heating and evaporating moisture in the black ink droplets on the continuous paper P.

When the control device 18 selects one or more of the infrared radiation devices 14, the control device 18

2017245346 11 Jul 2018 determines which of the infrared radiation devices 14A, 14B, and 14C is/are to be operated among the infrared radiation devices 14. When, for example, all of the infrared radiation devices 14A, 14B, and 14C are to be operated, each of the infrared radiation devices 14A, 14B, and 14C radiates infrared light (infrared laser) toward the continuous paper P onto which the black ink droplets have been ejected. Accordingly, moisture in the black ink droplets that have been ejected onto the continuous paper P is heated and evaporated, so that the continuous paper P is dried.

The image forming apparatus 10 includes three infrared radiation devices 14A, 14B, and 14C disposed between the four recording heads 12K, 12C, 12M, and 12Y of the respective colors, and the drying device 16 disposed downstream of the most downstream recording head 12Y. Accordingly, the structure of the image forming apparatus 10 is simpler than the structure in which drying is performed only by infrared radiation devices that are each disposed downstream of a corresponding one of ink droplet ejection heads of the respective colors.

In the image forming apparatus 10, the recording heads 12K, 12C, and 12M other than the most downstream recording head 12Y each eject ink containing an infrared absorbent or black ink. Therefore, in the image forming apparatus 10, the continuous paper P onto which the inks have been ejected by the recording heads 12K, 12C, and 12M of the respective colors can be pre-dried by the infrared radiation devices 14A, 14B,

2017245346 11 Jul 2018 and 14C that are respectively disposed downstream of the recording heads 12K, 12C, and 12M of the respective colors.

In the image forming apparatus 10, the most downstream recording head 12Y ejects ink containing no infrared absorbent Therefore, in the image forming apparatus 10, color turbidity of the yellow ink ejected by the most downstream recording head 12Y is lower than that in the case where the most downstream ink droplet ejection head ejects ink containing an infrared absorbing material.

In the image forming apparatus 10, the ink containing no infrared absorbent is light-colored ink (that is, yellow ink). Therefore, in the image forming apparatus 10, color turbidity of the light-colored ink is lower than that in the case where the ink containing an infrared absorbing material is lightcolored ink.

When the image forming apparatus 10 forms a monochrome image, selective operation of either one or more of the infrared radiation devices 14 or the drying device 16 is performed. Therefore, in the image forming apparatus 10, unlike the case where the selective operation of either one or more of the infrared radiation devices or the drying device is not performed when a monochrome image is formed, the continuous paper P onto which the black ink has been ejected can be dried by one or more of the infrared radiation devices 14 or the drying device 16 as appropriate. More specifically, in the image forming apparatus 10, unlike the case where the selective operation of either one or more of the infrared

2017245346 11 Jul 2018 radiation devices or the drying device is not performed when a monochrome image is formed, spreading of the ink and deformation of the continuous paper P can be reduced by selecting the operation of one or more of the infrared radiation devices 14, and continuous paper P having an absorption wavelength in the infrared range can be processed by selecting the operation of the drying device 16. Furthermore, the operating cost of the image forming apparatus is lower than that in the case where the selective operation of either one or more of the infrared radiation devices or the drying device is not performed when a monochrome image is formed.

In the image forming apparatus 10, when a monochrome image is formed by using the black ink ejected from the recording head 12K, the number of infrared radiation devices to be operated among the infrared radiation devices 14A, 14B, and 14C and the position of each infrared radiation device to be operated are selectable. Therefore, in the image forming apparatus 10, unlike the case where only one ink droplet ejection head that ejects ink containing an infrared absorbing material is disposed downstream of the ink droplet ejection head that ejects the black ink, an appropriate drying mode for drying the continuous paper P onto which the black ink has been ejected can be selected.

In the image forming apparatus 10, the recording heads 12K, 12C, 12M, and 12Y of the respective colors eject aqueous inks. Therefore, in the image forming apparatus 10, the

2017245346 11 Jul 2018 recording heads 12K, 12C, 12M, and 12Y of the respective colors eject aqueous inks more easily than in the case where the ink droplet ejection heads of respective colors eject oil based inks .

In the present exemplary embodiment, the image forming apparatus 10 forms an image on the continuous paper P. However, the present invention is not limited to the continuous paper P. For example, the present invention may also be applied to an image forming apparatus that forms an image on successively transported sheets of paper. Also, the recording medium on which an image is formed is not limited t paper, and may instead be, for example, a film.

The image forming apparatus 10 according to the present exemplary embodiment includes the recording heads 12K, 12C,

12M, and 12Y that respectively eject black ink, cyan ink, magenta ink, and yellow ink. However, the present invention is not limited to this. For example, the colors of inks may be changed to different colors, and an ink droplet ejection head that ejects another ink may be additionally provided.

For example, the image forming apparatus may include five ink droplet ejection heads that eject white ink in addition to black ink, cyan ink, magenta ink, and yellow ink.

The image forming apparatus may include five ink droplet ejection heads that eject black ink, cyan ink, magenta ink, yellow ink, and white ink, and the ink droplet ejection head that ejects white ink may be disposed at the most downstream position. In this structure, for example, the white ink may

2017245346 11 Jul 2018 be the ink containing no infrared absorbing material, and the yellow ink, which is ejected from an ink droplet ejection head that is upstream of the white ink droplet ejection head, may be ink containing an infrared absorbing material.

In the image forming apparatus 10 according to the present exemplary embodiment, two or more recording heads 12C and 12M that each eject ink containing an infrared absorbing material are disposed downstream of the recording head 12K that ejects black ink. However, the present invention is not limited to this. For example, the recording head 12K that ejects black ink may instead be disposed at another position that is not the most downstream position.

Examples

An experiment is performed to study the quality of an image formed by the image forming apparatus and the relationships between the laser intensity of an infrared radiation device and the temperature reached by an image formed of ink droplets on the continuous paper P and between the laser intensity of the infrared radiation device and the amount of moisture remaining in the continuous paper P.

In this experiment, the distances between the recording heads 12K, 12C, 12M, and 12Y of the image forming apparatus 10 (for example, the distance from an upstream side surface of the recording head 12K to an upstream side surface of the adjacent recording head 12C) are set to 100 mm (0.96 sec in terms of the speed of the continuous paper P). The length of the infrared radiation devices 14 in the transporting

2017245346 11 Jul 2018 direction of the continuous paper P is 20 mm (0.19 sec in terms of the speed of the continuous paper P).

ORTHO (manufactured by 0 j i Paper Co., Ltd.) is used as the continuous paper P. Inks of two colors, which are cyan and magenta, are used, and the cyan ink and magenta ink are ejected in that order. Ink droplets have a volume of 2.0 pi, and the density thereof is 1200 dpi (dot per inch). The transport speed of the continuous paper P is 6.25 m/min.

A two-color image is formed by using the image forming apparatus 10. As a result, the ink droplets on the continuous paper P reach a temperature of 60°C to 65°C immediately after passing the infrared radiation device 14B behind the recording head that ejects the cyan ink, and reach a temperature of 80°C to 85°C immediately after passing the infrared radiation device 14C behind the recording head that ejects the magenta ink.

The qualities of images obtained when the infrared radiation devices radiate lasers and when the infrared radiation devices do not radiate lasers (when only the drying device 16 is used) are studied. The result shows that when the infrared radiation devices radiate lasers, the occurrences of distortion of lines in an image, feathering, such as ink bleeding, and color mixture are lower than those when the infrared radiation devices do not radiate lasers.

Fig. 3 is a graph showing the temperature reached by an image formed of ink droplets on the continuous paper P and the amount of moisture remaining in the continuous paper P

2017245346 11 Jul 2018 relative to the laser intensity of an infrared radiation device. Referring to Fig. 3, the temperature reached by the image on the continuous paper P and the amount of moisture remaining in the continuous paper P are measured while changing the laser intensity of the infrared radiation device. In this experiment, black ink K365 is used, and OKT110 (manufactured by 0ji Paper Co., Ltd.) is used as the continuous paper P. The ink droplets have a volume of 2.0 pi.

Fig. 3 shows that image degradation can be reduced by evaporating 30% to 50% of moisture in the ink droplets by laser radiation from the infrared radiation devices 14 disposed between the recording heads of the respective colors.

Although a specific exemplary embodiment of the present invention has been described in detail, the present invention is not limited to the above-described exemplary embodiment.

It is obvious to a person skilled in the art that various other exemplary embodiments are possible within the scope of the present invention. In the foregoing description, a power supply for each laser element unit and a signal wiring diagram are omitted.

The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain

2017245346 11 Jul 2018 the principles of the invention and its practical applications thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated It is intended that the scope of the invention be defined by the following claims and their equivalents.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word comprise or variations such as comprises or comprising is used in an inclusive sense, i.e to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

2017245346 11 Jul 2018

Claims

Claims

1. An image forming apparatus comprising:

a plurality of ink droplet ejection heads of respective colors, the ink droplet ejection heads being arranged in a transporting direction of a recording medium and ejecting inks of different colors toward the recording medium;

an infrared radiation device that is disposed between the ink droplet ejection heads of the respective colors and that radiates infrared light toward ink droplets on the recording medium; and a drying device that is disposed downstream of one of the ink droplet ejection heads of the respective colors that is most downstream in the transporting direction of the recording medium, the drying device drying the recording medium by heating the recording medium; and a control device that selectively controls the operation of the infrared radiation device to evaporate 30% to 50% of moisture in the ink droplets.
2. The image forming apparatus according to Claim 1, wherein one or more of the ink droplet ejection heads other than the most downstream ink droplet ejection head each eject ink containing an infrared absorbing material or black ink.
3. The image forming apparatus according to Claim 1 or 2, wherein the most downstream ink droplet ejection head ejects

2017245346 11 Jul 2018 ink containing no infrared absorbing material.
4. The image forming apparatus according to Claim 3, wherein the ink containing no infrared absorbing material is light-colored ink.
5. The image forming apparatus according to any one of Claims 1 to 4, wherein one of the ink droplet ejection heads that ejects black ink is not the most downstream ink droplet ejection head, and wherein, when a monochrome image is formed by using the black ink ejected from the ink droplet ejection head that ejects the black ink, either the infrared radiation device or the drying device is selectively operated.
6. The image forming apparatus according to Claim 5, wherein two or more ink droplet ejection heads that eject ink containing an infrared absorbing material are disposed downstream of the ink droplet ejection head that ejects the black ink, and wherein, when the monochrome image is formed by using the black ink ejected from the ink droplet ejection head that ejects the black ink, the number of infrared radiation devices to be operated and a position of each infrared radiation device to be operated are selectable.
7. The image forming apparatus according to any one of

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Claims 1 to 6, wherein the inks of different colors ejected from the ink droplet ejection heads of the respective colors are aqueous inks .

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FIG. 3

REACHED TEMPERATURE [°C]

AMOUNT OF REMAINING MOISTURE [%]

LASER INTENSITY [J/cm²]