JP2023063945A - Image recording method and image recording apparatus - Google Patents

Abstract

To provide an image recording method and an image recording apparatus for suppressing uneven drying of an image formed on a recording medium supported by a guide surface.SOLUTION: There is provided an image recording method which comprises: a conveying step of supporting a recording medium by a guide surface to convey the recording medium together with the guide surface; an image forming step of ejecting a liquid from a liquid ejection head onto the conveyed recording medium to form an image; and a preheating step of preheating the recording medium prior to the image forming step, wherein when the temperature of the guide surface in the image forming step is defined as TG and the temperature of the recording medium is defined as TP, the drying irregularities are suppressed by the image recording method having the relationship of 0≤TG-TP≤1.2[°C].SELECTED DRAWING: Figure 13

Description

The present invention relates to an image recording method and image recording apparatus, and more particularly to a technique for recording an image on a recording medium supported on a guide surface.

2. Description of the Related Art An inkjet recording apparatus is known that ejects ink from an inkjet head onto a recording medium conveyed by a conveying unit to record an image on the recording medium. The guide surface of the transport unit that supports the recording medium may be provided with a plurality of unevenness depending on the application.

Japanese Patent Application Laid-Open No. 2002-200002 discloses an ink jet recording apparatus that includes a paper carrying drum that carries and conveys a paper, which is a recording medium, on its outer peripheral surface, and an ink ejection unit that ejects ink toward the paper carried by the paper carrying drum. An apparatus is disclosed. The paper carrying drum has suction holes on the outer peripheral surface thereof, and when the suction device operates, a suction force is generated to attract the paper to the suction holes.

Japanese Patent No. 6850429

However, in the inkjet recording apparatus described in Patent Document 1, there is a problem that uneven drying occurs due to differences in heat transfer between the suction holes on the outer peripheral surface of the paper carrying drum and the portion other than the suction holes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image recording method and an image recording apparatus capable of suppressing uneven drying of an image formed on a recording medium supported by a guide surface.

One aspect of an image recording method for achieving the above object comprises a conveying step of supporting a recording medium on a guide surface and conveying the recording medium integrally with the guide surface; An image forming step of ejecting to form an image, and a preheating step of preheating the recording medium prior to the image forming step, wherein T _G is the temperature of the guide surface and T is the temperature of the recording medium in the image forming step. This image recording method has a relationship of 0≦T _G -T _P ≦1.2 [° C.], where _P. According to this aspect, drying unevenness of an image formed on the recording medium supported by the guide surface can be suppressed.

It is preferable to have a relationship of 0≦T _G −T _P ≦1.0 [° C.]. Thereby, drying unevenness can be further suppressed.

Preferably, the temperature of the recording medium is the temperature of the recording medium at the position where the liquid is applied, and the temperature of the guide surface is the temperature of the guide surface at the position where the liquid is applied and the position of the recording medium. When the temperature _TP of the position of the recording medium to which the liquid is applied and the temperature _TG of the guide surface at the position integral with that position are within the above ranges, the liquid applied to the recording medium does not move. Since it dries, uneven drying of the formed image can be suppressed.

A treatment liquid application process of applying a treatment liquid to a recording medium prior to an image forming process, a switching process of switching whether or not the treatment liquid application process is performed, and a recording medium coated with the treatment liquid when the treatment liquid application process is performed. It is preferable to include a treatment liquid drying process for heating the treatment liquid drying process, which also serves as a preheating process regardless of the presence or absence of the treatment liquid coating process. When the treatment liquid is applied, uneven drying can be suppressed by the treatment liquid, and when the treatment liquid is not applied, uneven drying can be suppressed by pre-drying T _G and T _P within the above ranges. can.

The guide surface may have at least one of a protrusion and a hole. According to this aspect, uneven drying can be suppressed even with the guide surface having at least one of the convex portion and the hole portion. At least one of a large number of protrusions and holes may be arranged two-dimensionally on the guide surface.

In the conveying step, it is preferable to support the recording medium using the peripheral surface of the drum that rotates about the axis as a guide surface. According to this aspect, even if the peripheral surface of the drum that rotates around the axis is the guide surface, uneven drying can be suppressed.

A liquid drying process for drying the liquid may be provided after the image forming process. According to this aspect, even when the temperature of the guide surface rises due to the influence of the liquid drying process, uneven drying can be suppressed.

It is preferable that the method includes a temperature measuring step of measuring the temperature of the recording medium, and the preheating step preheats the recording medium based on the measured temperature. Thereby, _TG and _TP in the image forming process can be controlled within the above ranges. In the temperature measurement step, the temperature of the guide surface may be measured.

One aspect of an image recording apparatus for achieving the above object includes a transport mechanism that supports a recording medium on a guide surface and transports the recording medium integrally with the guide surface; and a preheating mechanism for preheating a recording medium before recording an image, wherein T _G is the temperature of the guide surface when recording the image, and T _P is the temperature of the recording medium. Then, the image recording apparatus has a relationship of 0≦T _G −T _P ≦1.2 [° C.]. According to this aspect, drying unevenness of an image formed on the recording medium supported by the guide surface can be suppressed.

The preheating mechanism preferably includes a fan that supplies dry air to the recording medium. Thereby, the recording medium can be preheated by the dry air.

A drying mechanism for drying the ejected liquid may be provided. According to this aspect, even when the temperature of the guide surface rises due to the influence of the drying mechanism, uneven drying can be suppressed.

According to the present invention, uneven drying of an image formed on a recording medium supported by a guide surface can be suppressed.

FIG. 1 is a schematic diagram showing an example of a guide surface. FIG. 2 is a cross-sectional view of the guide surface and paper when the paper is supported by the guide surface and ink is applied. FIG. 3 is a top view of the paper. FIG. 4 is a schematic diagram showing an example of a guide surface. FIG. 5 is a cross-sectional view of the guide surface and paper when the paper is supported by the guide surface and ink is applied. FIG. 6 is a top view of the paper. FIG. 7 is an overall configuration diagram showing a schematic configuration of an inkjet recording apparatus. FIG. 8 is a perspective view showing the configuration of the tip portion of the inkjet head. FIG. 9 is a partially enlarged view of the nozzle surface. FIG. 10 is a plan view of the nozzle surface of the head module. FIG. 11 is a longitudinal sectional view showing the three-dimensional structure of the ejector. FIG. 12 is a functional block diagram of the control system of the inkjet recording apparatus. FIG. 13 is a graph showing the relationship between the difference in the temperature of the peripheral surface of the image forming drum and the temperature of the paper, and the visibility of uneven drying.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<Occurrence of uneven drying>
An image recorded (image formed) by an inkjet recording apparatus may have drying unevenness. Drying unevenness is a phenomenon in which shading occurs in an image, and includes a phenomenon in which a part of an image appears dark and a phenomenon in which colors appear white and pale. Drying unevenness is caused by movement of landed ink on a recording medium.

Conventionally, fluidity is suppressed by increasing the viscosity of the ink by applying a treatment liquid onto the recording medium in a process prior to ejecting the ink. On the other hand, when the treatment liquid is not applied, the ink tends to move. In the following, the case where the treatment liquid is not applied will be described.

Ink migration tends to occur when the temperature distribution on the recording medium is uneven. If the temperature distribution is non-uniform, the ink dries easily at high temperatures and is difficult to dry at low temperatures. Where the ink dries easily, the ink becomes concentrated and the surface tension increases. On the contrary, in a place where the ink is difficult to dry, the surface tension becomes relatively small because the ink is not so concentrated. Due to this difference in surface tension, the ink moves from an area where the surface tension is low to an area where the surface tension is high, resulting in uneven drying.

The inventors of the present application have found that there is a problem that non-uniform temperature distribution occurs due to the shape of the guide surface of the transport unit, resulting in uneven drying. For example, if the guide surface has unevenness, the contact with the recording medium becomes uneven due to the unevenness, and the degree of heat transfer to the recording medium varies depending on the contact location.

A guide surface of a transport unit that contacts and supports a recording medium during image formation may have an uneven shape. FIG. 1 is a schematic diagram showing an example of a guide surface 10 that supports a recording medium. The guide surface 10 shown in FIG. 1 has a plurality of protrusions 12 and a plurality of holes 14 . The projection 12 has a cylindrical shape with a diameter of 1.0 mm and a height of 0.1 mm. The convex portions 12 are two-dimensionally arranged at regular intervals in the vertical direction and in the horizontal direction perpendicular to the vertical direction. The hole portion 14 is a through hole having a diameter of 1.0 mm that penetrates the guide surface 10 . The holes 14 are two-dimensionally arranged at regular intervals in the vertical and horizontal directions.

FIG. 2 is a cross-sectional view of the guide surface 10 and the paper P when the paper P, which is an example of a recording medium, is supported by the guide surface 10 and the ink I is applied. is shown. FIG. 3 is a top view of the paper P and shows drying unevenness when a solid image is formed on the paper P supported by the guide surface 10 . A solid image is an image with an ink coverage of more than 100%. Here, consider a case where the temperature of the guide surface 10 is relatively higher than the temperature of the recording medium.

Since the guide surface 10 is made of a material that has a relatively high thermal conductivity compared to the surrounding air, heat is easily transferred to the portion of the paper P that contacts the convex portion 12 (the position corresponding to the convex portion 12). , the temperature of the portion of the paper P that is in contact with the convex portion 12 is locally high. Therefore, the temperature of the position of the paper P that contacts the convex portion 12 is relatively higher than that of the position that does not contact the convex portion 12 . For this reason, as shown in FIG. 2, the ink I applied to the paper P is accelerated to dry and concentrate at the positions of the paper P that are in contact with the protrusions 12, and the surface tension is increased relative to the positions that are not in contact. grow to Due to this surface tension difference, the ink moves from a place where the surface tension is small to a place where the surface tension is large, and the ink concentrates on the position of the paper P that is in contact with the convex portion 12 .

As a result, as shown in FIG. 3, drying unevenness in which the density of a part of the image becomes relatively high occurs. It should be noted that in FIG. 3, the portion with high density is emphasized. A portion with relatively high density is a portion where ink is concentrated. In the example shown in FIG. 3, the portions with relatively high density occur corresponding to the positions of the convex portions 12, and are circular with a diameter of approximately 1.0 mm.

Also, the guide surface of the transport unit may have a plurality of holes. FIG. 4 is a schematic diagram showing an example of the guide surface 20 that supports the paper P. As shown in FIG. The guide surface 20 shown in FIG. 4 has a plurality of holes 22 . The hole portion 22 is a through hole having a diameter of 0.5 mm that passes through the guide surface 20 . The holes 22 are two-dimensionally arranged at regular intervals in the vertical and horizontal directions.

FIG. 5 is a cross-sectional view of the guide surface 20 and the paper P when the paper P is supported by the guide surface 20 and the ink I is applied. FIG. 6 is a top view of the paper P and shows drying unevenness when a solid image is formed on the paper P supported by the guide surface 20 . Here, similarly, consider a case where the temperature of the guide surface 10 is relatively higher than the temperature of the recording medium.

Since the hole 22 (air) of the guide surface 20 has a relatively low thermal conductivity compared to the material of the guide surface 20, the paper P is in contact with the air of the hole 22 (corresponding to the hole 22). position). Therefore, the position corresponding to the hole 22 of the paper P has a relatively lower temperature than the position in contact with the guide surface 20 . For this reason, as shown in FIG. 5, the ink I applied to the paper P is not dried and concentrated at the positions of the paper P corresponding to the hole portions 22, and is Surface tension becomes relatively small. Due to this difference in surface tension, the ink moves from a place where the surface tension is low to a place where the surface tension is high, and the ink at the position of the paper P corresponding to the hole 22 is diffused and reduced.

As a result, as shown in FIG. 6, uneven drying occurs in which part of the image becomes white and the density becomes relatively low. In addition, in FIG. 6, the portions with low density are emphasized. A portion with relatively low density is a portion with less ink. In the example shown in FIG. 6, the portions with relatively low density are generated corresponding to the positions of the holes 22, and are circular with a diameter of approximately 0.5 mm.

In order to solve the above problems, it is effective to reduce the fluidity of the ink by suppressing the heat conduction from the guide surface to the recording medium to improve the drying unevenness.

Here, in order to suppress the heat conduction, two countermeasures are conceivable: "use a guide surface made of a material with low thermal conductivity" or "minimize the temperature difference between the guide surface and the recording medium". However, it is unrealistic to use a material having thermal conductivity equivalent to that of air for the guide surface of the transport unit. Therefore, in order to suppress the heat conduction from the guide surface to the recording medium, it can be said that the temperature of the guide surface and the recording medium is reduced as much as possible as a practical solution. Specifically, it is the addition of a function for adjusting the temperature of the guide surface or the recording medium. An image recording method and an image recording apparatus for adjusting the temperature of a recording medium will be described below.

<Inkjet recording device>
〔overall structure〕
FIG. 7 is an overall configuration diagram showing a schematic configuration of the inkjet recording apparatus 100. As shown in FIG. The inkjet recording device 100 is a sheet-fed printing device (an example of an “image recording device”) that prints a color image on a sheet of paper P. As shown in FIG. The paper P is ordinary paper such as high-quality copy paper.

As shown in FIG. 7 , the inkjet recording apparatus 100 includes a paper feeding section 110 , a treatment liquid application section 120 , a treatment liquid drying section 130 , an image forming section 140 , an ink drying section 200 and a stacking section 240 .

[Paper feed section]
The paper feed unit 110 automatically feeds the paper P one by one. The paper feeding unit 110 includes a paper feeding device 112 , a feeder board 114 and a paper feeding drum 116 . The paper feeder 112 takes out the paper sheets P set in the paper feed tray 112</b>A in the state of a bundle one by one from the top and feeds them to the feeder board 114 . The feeder board 114 transfers the paper P received from the paper feeder 112 to the paper feed drum 116 .

The paper feed drum 116 receives the paper P fed from the feeder board 114 and transfers the received paper P to the treatment liquid coating section 120 .

[Treatment liquid coating part]
The treatment liquid application unit 120 applies the treatment liquid to the paper P. As shown in FIG. The treatment liquid is a liquid having a function of aggregating, insolubilizing, or increasing the viscosity of the coloring material component in the ink. The treatment liquid application unit 120 includes a treatment liquid application drum 122 and a treatment liquid application device 124 .

The treatment liquid coating drum 122 receives the paper P from the paper feed drum 116 and transfers the received paper P to the treatment liquid drying section 130 . The treatment liquid coating drum 122 is provided with a gripper 123 on its peripheral surface. The gripper 123 is used to grip the leading edge of the paper P, rotates, and conveys the paper P wound around its peripheral surface.

The treatment liquid coating device 124 applies the treatment liquid to the conveyed paper P using the treatment liquid coating drum 122 (an example of the “treatment liquid coating step”). The treatment liquid is applied using a roller.

The inkjet recording apparatus 100 has a mode in which the paper P is coated with the treatment liquid and a mode in which the paper P is not coated with the treatment liquid. On the other hand, the treatment liquid application unit 120 is configured to be able to switch between application and non-application of the treatment liquid to the paper P. FIG. When the paper P is not to be coated with the treatment liquid, the roller for applying the treatment liquid is retracted from the paper P transport path.

[Treatment liquid drying part]
The treatment liquid drying section 130 (an example of a “preheating mechanism”) dries the paper P coated with the treatment liquid. The treatment liquid drying section 130 includes a treatment liquid drying drum 132 , a warm air blower 134 , a warm air blower 135 and a warm air blower 136 . The treatment liquid drying drum 132 receives the paper P from the treatment liquid coating drum 122 and transfers the received paper P to the image forming section 140 . The processing liquid drying drum 132 has a gripper 133 on its peripheral surface. The treatment liquid drying drum 132 uses a gripper 133 to grip the leading edge of the paper P, rotates, and transports the paper P. As shown in FIG.

The warm air blower 134 is installed at a position facing the peripheral surface of the treatment liquid coating drum 122 . The warm air blower 134 is non-contact heating means for blowing air heated and dried by a heater (not shown) from an outlet (not shown) by a fan (not shown). The hot air blower 134 blows dry air (warm air) of 30 to 50° C. onto the paper P conveyed using the treatment liquid coating drum 122 to dry the treatment liquid (an example of a “preheating step”). .

The warm air blower 135 and the warm air blower 136 are installed inside the treatment liquid drying drum 132, respectively. The configurations of the warm air blower 135 and the warm air blower 136 are similar to that of the warm air blower 134 . The warm air blower 135 and the warm air blower 136 blow drying air (warm air) of 30 to 50° C. onto the paper P conveyed by the treatment liquid drying drum 132 to dry the treatment liquid. In the present embodiment, the treatment liquid is supplied by a hot air blower 134 installed at a position facing the circumferential surface of the treatment liquid coating drum 122 , and a warm air blower 135 and a warm air blower 136 installed inside the treatment liquid drying drum 132 . However, the number of hot air blowers and their positions are not particularly limited.

As will be described later, the treatment liquid drying unit 130 blows dry air onto the paper P regardless of whether the treatment liquid is applied to the paper P or not. The temperature of the drying air may be changed depending on whether or not the treatment liquid is applied.

[Image forming section]
The image forming section 140 includes an image forming drum 142 , a head unit 144 and a scanner 190 . The image forming drum 142 (an example of a “conveyance mechanism”) is a cylindrical member having a rotation shaft (not shown). The image forming drum 142 receives the paper P from the treatment liquid drying drum 132, and rotates around the rotation shaft to transfer the received paper P to the ink drying section 200 (an example of a “conveying step”). A peripheral surface 142A corresponding to a guide surface of the image forming drum 142 is made of SUS (Steel Use Stainless).

The imaging drum 142 has a gripper 143 on its peripheral surface 142A. The image forming drum 142 uses a gripper 143 to grip the leading edge of the paper P, rotates, winds the paper P around a peripheral surface 142A (an example of a “guide surface”), and wraps the back surface of the paper P around the peripheral surface 142A. It is supported and transported integrally with the peripheral surface. The image forming drum 142 has an adsorption mechanism (not shown), and adsorbs the paper P wound around the peripheral surface to the peripheral surface 142A.

Negative pressure is used for adsorption. The image forming drum 142 has a large number of suction holes (for example, the holes 14 in FIG. 1) on the peripheral surface 142A, and suction is performed from the inside through the suction holes to adsorb the paper P to the peripheral surface 142A. Static electricity may be used for adsorption. In this case, the attraction is performed by charging the image forming drum 142 .

The image forming drum 142 may have a large number of protrusions (for example, the protrusions 12 in FIG. 1) for preventing the paper P from being wrinkled on the peripheral surface 142A.

The head unit 144 includes an inkjet head 146C (an example of a “liquid ejection head”) that ejects cyan (C) ink (an example of “liquid”), an inkjet head 146M that ejects magenta (M) ink, and a yellow (Y) ink. ) and an inkjet head 146K for ejecting black (K) ink.

Each of the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K is arranged at regular intervals on the transport path of the paper P using the image forming drum 142 .

From the nozzles 162 (see FIG. 10) of the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K (an example of a "liquid ejection head") toward the paper P transported using the image forming drum 142 When the ink is ejected, an image is recorded on the surface of the paper P (an example of the "image forming process").

Although the configuration using four colors of ink, cyan, magenta, yellow, and black, is exemplified here, the combination of ink colors and the number of colors is not limited to this embodiment, and light ink may be used as necessary. , dark ink, and special color ink may be added.

The scanner 190 reads an image recorded on the paper P using the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K.

[Ink drying part]
The ink drying section 200 (an example of a “drying mechanism”) performs a drying process on the paper P on which an image has been recorded using the image forming section 140 (an example of a “liquid drying step”). The ink drying section 200 includes a chain delivery 210 , a paper guide 220 , a warm air blower 230 and a paper detection sensor 232 .

The chain delivery 210 receives the paper P from the image forming drum 142 and transports the received paper P to the stacking section 240 . The chain delivery 210 includes a pair of endless chains 212 that travel along a prescribed travel route, grips the leading edge of the paper P using grippers 214 provided on the pair of chains 212, and delivers the paper P along the prescribed route. Convey along the conveying route. A plurality of grippers 214 are provided at regular intervals along the running direction of the chain 212 .

The paper guide 220 is a member that guides the conveyance of the paper P using the chain delivery 210 . The paper guide 220 is composed of a first paper guide 222 and a second paper guide 224 .

The first paper guide 222 guides the paper P to be transported through the first transport section of the chain delivery 210 . The second paper guide 224 guides the paper to be conveyed through the second conveying section after the first conveying section.

The hot air blower 230 blows hot air onto the paper P conveyed using the chain delivery 210 . Note that the image forming drum 142 may be heated by the influence of the hot air from the hot air blower 230, and the temperature of the peripheral surface 142A may rise.

A paper detection sensor 232 detects the presence or absence of paper P. FIG. Examples of the paper detection sensor 232 include a reflective optical sensor or a transmissive optical sensor.

[Collecting part]
The stacking unit 240 includes a stacking device 242 . The stacking section 240 includes a stacking device 242 that receives the paper P conveyed from the ink drying section 200 using the chain delivery 210 and stacks the paper P. Chain delivery 210 releases paper P at a predetermined stacking position.

The stacking device 242 includes a stacking tray 244 . The stacking device 242 receives the paper P released from the chain delivery 210 and stacks the paper P on the stacking tray 244 in a bundle.

<Configuration example of inkjet head>
〔overall structure〕
The inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K can apply the same configuration. In the following description, the inkjet head 146C will be described as a representative.

FIG. 8 is a perspective view showing the configuration of the tip portion of the inkjet head 146C. The inkjet head 146C is a line-type liquid ejection head having a nozzle array capable of recording an image with a prescribed recording resolution over the entire recording area of the paper P in one scan in the width direction of the paper P. Such a liquid ejection head is also called a full-line liquid ejection head or a page wide head. The width direction of the paper P is a direction orthogonal to the transport direction of the paper P and a direction parallel to the surface of the paper P. As shown in FIG.

A tip portion of the inkjet head 146C has a nozzle surface 148 . Nozzles 162 (see FIG. 10) for ejecting ink are formed on the nozzle surface 148 .

Also, the inkjet head 146C has a structure in which a plurality of head modules 150-i are connected in a row along the longitudinal direction. Note that i is an integer from 1 to n. In the following description, the head module 150-i may be referred to as the head module 150 by omitting the i representing the head module number of the head module 150-i.

The head module 150-i is attached to and integrated with the support frame 152. As shown in FIG. Each head module 150-i includes a cable 154 for electrical connection.

[Arrangement of nozzles]
1 is a partially enlarged view of the nozzle surface 148. FIG. Nozzle face 148-i of head module 150-i is a parallelogram. Dummy plates 156 are attached to both ends of the support frame 152 . The nozzle surface 148 of the inkjet head 146, together with the surface 156A of the dummy plate 156, is rectangular as a whole.

A strip-shaped nozzle arrangement portion 158-i is provided in the central portion of the nozzle surface 148-i of the head module 150-i. The nozzle arrangement portion 158-i functions substantially as a nozzle surface 148-i. Nozzle 162 is provided in nozzle placement portion 158-i. Note that FIG. 9 does not show individual nozzles 162, but shows a nozzle row 160 composed of a plurality of nozzles.

FIG. 10 is a plan view of the nozzle surface 148-i of the head module 150-i. The Y direction in FIG. 10 represents the transport direction of the paper P, and the X direction represents the width direction of the paper P. As shown in FIG. A plurality of nozzles 162 are two-dimensionally arranged on the nozzle surface 148-i of the head module 150-i.

The head module 150-i has an end surface on the long side along the V direction inclined at an angle β with respect to the width direction of the paper P, and an end surface on the long side along the direction V inclined at an angle α with respect to the transport direction of the paper P. It has a planar shape of a parallelogram with short side end faces along the edges.

In the head module 150-i, a plurality of nozzles 162 are arranged in a matrix in the row direction along the V direction and the column direction along the W direction. The nozzles 162 may be arranged along the row direction along the width direction of the paper P and along the column direction that obliquely intersects the width direction of the paper P.

In the case of the inkjet head 146C, a projected nozzle array obtained by projecting the nozzles 162 along the X direction is equivalent to a single nozzle array in which the nozzles 162 are arranged at approximately equal intervals at a nozzle density that achieves the maximum recording resolution in the X direction. can be thought of as The term “substantially evenly spaced” means that the droplet ejection points that can be recorded by the inkjet recording apparatus 100 are substantially equally spaced. For example, the concept of equidistant spacing may be used even if the spacing is slightly different in consideration of at least one of manufacturing error and movement of droplets on the paper P due to landing interference. include.

The arrangement form of the nozzles of the inkjet head 146 is not limited, and various nozzle arrangement forms can be adopted. For example, instead of a matrix-like two-dimensional arrangement, a straight line arrangement, a V-shaped nozzle arrangement, and a zigzag arrangement such as a W-shaped arrangement in which the V-shaped arrangement is a repeating unit are also possible. .

[Construction of ejector]
FIG. 11 is a longitudinal sectional view showing the three-dimensional structure of the ejector 164. As shown in FIG. Ejector 164 includes nozzle 162 , pressure chamber 166 leading to nozzle 162 , and piezoelectric element 168 . Nozzle 162 communicates with pressure chamber 166 via nozzle channel 170 . The pressure chamber 166 communicates with a supply-side common branch passage 174 via an individual supply passage 172 .

A vibration plate 176 forming the top surface of the pressure chamber 166 includes a conductive layer (not shown) functioning as a common electrode corresponding to the lower electrode of the piezoelectric element 168 . The pressure chamber 166, walls of other flow path portions, diaphragm 176, and the like can be made of silicon.

The material of diaphragm 176 is not limited to silicon, and may be formed from a non-conductive material such as resin. The diaphragm 176 itself may be made of a metal material such as stainless steel, and may serve as a diaphragm that also serves as a common electrode.

The structure in which the piezoelectric element 168 is laminated on the vibration plate 176 constitutes a piezoelectric unimorph actuator. A driving voltage is applied to the individual electrode 178 that is the upper electrode of the piezoelectric element 168 to deform the piezoelectric body 180 and bend the vibration plate 176 to change the volume of the pressure chamber 166 . A change in pressure accompanying a change in volume of the pressure chamber 166 acts on the ink, and the ink is ejected from the nozzle 162 .

When the piezoelectric element 168 returns to its original state after the ink is discharged, the pressure chamber 166 is filled with new ink through the individual supply channel 172 from the supply side common branch channel 174 . The operation of filling the pressure chamber 166 with ink is called refilling.

The shape of the pressure chamber 166 in a plan view is not particularly limited, and various shapes such as a quadrangle, other polygons, a circle, or an ellipse are possible. A cover plate 182 is provided above the individual electrodes 178 . The cover plate 182 is a member that retains the movable space 184 of the piezoelectric element 168 and seals the periphery of the piezoelectric element 168 .

A supply side ink chamber (not shown) and a recovery side ink chamber (not shown) are formed above the cover plate 182 . The supply-side ink chamber is connected to a supply-side common main flow path (not shown) via a communication path (not shown). The recovery side ink chamber is connected to a recovery side common main flow path (not shown) via a communication path (not shown).

<Configuration of control system>
FIG. 12 is a functional block diagram of the control system of the inkjet recording apparatus 100. As shown in FIG. The inkjet recording apparatus 100 has a system controller 250 . The system controller 250 is a general control section that controls each section of the inkjet recording apparatus 100 in an integrated manner. The system controller 250 is an arithmetic unit that performs various kinds of arithmetic processing. The system controller 250 is a memory controller that controls data reading and data writing in memory.

[Communication part]
The inkjet recording apparatus 100 has a communication section 252 . The communication unit 252 transmits and receives data to and from a host computer 254 connected via a communication interface (not shown).

[Image memory]
The inkjet recording apparatus 100 has an image memory 256 . The image memory 256 functions as a temporary storage unit for various data including image data. Data is read from and written to the image memory 256 through the system controller 250 . Image data fetched from the host computer 254 via the communication unit 252 is stored in the image memory 256 .

[Conveyance control unit]
The inkjet recording apparatus 100 includes a transport control section 258 . A transport control unit 258 controls the operation of the transport unit 109 . The transport unit 109 includes the paper feed drum 116, the treatment liquid coating drum 122, the image forming drum 142, and the chain delivery 210 shown in FIG.

[Paper feed controller]
The inkjet recording apparatus 100 includes a paper feed controller 260 . The paper feed control unit 260 operates the paper feed unit 110 according to commands from the system controller 250 .

[Treatment liquid application controller]
The inkjet recording apparatus 100 includes a treatment liquid application control section 262 . The treatment liquid application control section 262 controls the operation of the treatment liquid application section 120 according to commands from the system controller 250 .

The treatment liquid application control unit 262 controls switching between application of the treatment liquid to the paper P by the treatment liquid application unit 120 (an example of a “switching step”) according to the set mode. The mode in which the treatment liquid is applied to the paper P and the mode in which the treatment liquid is not applied to the paper P may be switched by user input through the operation unit 272, or by determining the type of the paper P by a sensor (not shown). The need for the treatment liquid may be automatically determined and switched.

[Treatment liquid drying controller]
The inkjet recording apparatus 100 includes a treatment liquid drying control section 264 . The treatment liquid drying control section 264 controls the operation of the treatment liquid drying section 130 according to commands from the system controller 250 .

[Drawing control part]
The inkjet recording apparatus 100 includes an image formation control section 266 . The image forming control portion 266 controls the operation of the image forming portion 140 according to commands from the system controller 250 .

The image formation control section 266 includes an image processing section (not shown). The image processing unit forms dot data from input image data. The image processing section includes a color separation processing section (not shown), a color conversion processing section (not shown), a correction processing section (not shown), and a halftone processing section (not shown).

The color separation processing section performs color separation processing on the input image data. For example, when the input image data is represented by RGB (Red Green Blue), the input image data is decomposed into R, G, and B color data.

The color conversion processing unit converts image data for each color separated into R, G, and B into C, M, Y, and K corresponding to ink colors.

The correction processing unit performs correction processing on the image data converted into C, M, Y, and K for each color. Examples of correction processing include gamma correction processing, density unevenness correction processing, and abnormal recording element correction processing.

The halftone processing unit converts image data represented by multiple gradations, such as 0 to 255, into dot data represented by two values, or multivalues of three or more values less than the number of gradations of the input image data. Convert. The halftoning section applies predetermined halftoning rules. Examples of halftoning rules include dithering, error diffusion, and the like.

The image formation control unit 266 includes a waveform generation unit (not shown), a waveform storage unit (not shown), and a drive circuit (not shown). The waveform generator generates a waveform of the driving voltage. The waveform storage unit stores the waveform of the drive voltage.

A drive circuit generates a drive voltage having a drive waveform corresponding to dot data. The drive circuit supplies drive voltages to the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K shown in FIG.

That is, the ejection timing and ink ejection amount for each pixel position are determined based on the dot data generated through processing by the image processing unit. An ejection timing for each pixel position, a drive voltage corresponding to the ink ejection amount, and a control signal for determining the ejection timing for each pixel are generated. A driving voltage and a control signal are supplied to the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K, and the ink ejected from the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K is applied to the paper. A dot is formed in P.

[Ink drying controller]
The inkjet recording apparatus 100 includes an ink drying control section 268 . The ink drying control section 268 controls the operation of the ink drying section 200 according to commands from the system controller 250 .

[Integrated control part]
The inkjet recording apparatus 100 includes an accumulation control section 270 . The stacking control unit 270 controls the operation of the stacking unit 240 according to commands from the system controller 250 . The operation of the stacking unit 240 may include the opening and closing operation of the gripper 214 when stacking the image-formed sheets P in the stacking device 242 shown in FIG.

[Operation part]
The inkjet recording apparatus 100 has an operation section 272 . The operation unit 272 includes operation members such as operation buttons, a keyboard, and a touch panel. The operation unit 272 may include multiple types of operation members. Information input using the operation unit 272 is transmitted to the system controller 250 . The system controller 250 generates command signals for executing various processes according to information transmitted from the operation unit 272 . The system controller 250 transmits command signals to processing units that perform various processes.

[Display part]
The inkjet recording apparatus 100 has a display section 274 . The display unit 274 includes a display device (not shown) such as a liquid crystal panel and a display driver (not shown). The display unit 274 causes the display device to display various kinds of information such as various setting information of the apparatus and abnormality information in accordance with commands from the system controller 250 . The display unit 274 may be a touch panel type display device and may be used as the operation unit 272 as well.

[Parameter memory]
The inkjet recording apparatus 100 has a parameter storage section 276 . The parameter storage section 276 stores various parameters used in the inkjet recording apparatus 100 . Various parameters stored in the parameter storage unit 276 are read using the system controller 250 . Various parameters are set in each part of the apparatus using the system controller 250 .

[Program storage part]
The inkjet recording apparatus 100 has a program storage section 278 . The program storage section 278 stores programs used in each section of the inkjet recording apparatus 100 . Various programs stored in the program storage unit 278 are read out via the system controller 250 and executed in each unit of the apparatus.

[Sensor]
The inkjet recording apparatus 100 has a sensor 280 . Sensor 280 includes at least an optical sensor and a pressure sensor. Sensors 280 may include various sensors such as temperature sensors and flow sensors.

[Hardware configuration of various control units]
Various controllers shown in FIG. 12 are applied with a processor. The hardware structure of the processor is various processors as shown below. Various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and acts as various functional units, a GPU (Graphics Processing Unit), which is a processor specialized for image processing, Circuits specially designed to execute specific processes such as PLDs (Programmable Logic Devices), ASICs (Application Specific Integrated Circuits), etc. Also included are dedicated electrical circuits, which are processors with configuration, and the like.

One processing unit may be composed of one of these various processors, or two or more processors of the same or different type (for example, a plurality of FPGAs, a combination of CPU and FPGA, or a combination of CPU and GPU). Also, a plurality of functional units may be configured by one processor. As an example of configuring a plurality of functional units in a single processor, first, as represented by a computer such as a client or server, a single processor is configured by combining one or more CPUs and software. There is a form in which a processor acts as a plurality of functional units. Secondly, as typified by SoC (System On Chip), etc., there is a mode of using a processor that implements the functions of the entire system including a plurality of functional units with a single IC (Integrated Circuit) chip. In this way, various functional units are configured using one or more of the above various processors as a hardware structure.

Further, the hardware structure of these various processors is, more specifically, an electric circuit combining circuit elements such as semiconductor elements.

The processor executes instructions stored in a memory (not shown). The memory stores instructions for the processor to execute. The memory includes RAM (Random Access Memory) and ROM (Read Only Memory), which are not shown. The processor uses RAM as a work area, executes software using various programs and parameters including a research support program stored in ROM, and uses parameters stored in ROM etc. to perform various processes. to run.

<Action of Inkjet Recording Apparatus>
The inkjet recording apparatus 100 heats the paper P by the treatment liquid drying unit 130, supports the preheated paper P on the peripheral surface 142A of the image forming drum 142, and conveys the paper P integrally with the peripheral surface 142A. An image recording method is performed in which ink is ejected from the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K to form an image on the paper P transported by the . According to this image recording method, since the paper P is preheated by the treatment liquid drying section 130, the temperature difference between the peripheral surface 142A of the image forming drum 142 and the paper P can be relatively reduced when forming an image. can. Therefore, heat conduction from the peripheral surface 142A to the paper P can be suppressed, and the fluidity of the ink can be reduced, so that uneven drying can be suppressed.

In addition, the inkjet recording apparatus 100 performs an image recording method in which the processing liquid drying control unit 264 switches between the presence and absence of the processing liquid application step. When the treatment liquid application step is provided, the treatment liquid is applied to the paper P in the treatment liquid application unit 120 before the image formation step, and the paper P coated with the treatment liquid is preheated in the treatment liquid drying unit 130. (an example of the “processing liquid drying step”). If the treatment liquid application process is not included, the treatment liquid drying control section 264 preheats the paper P in the treatment liquid drying section 130 (an example of a "preheating process").

According to this image recording method, when the treatment liquid is applied, uneven drying can be suppressed by the treatment liquid. In addition, when the treatment liquid is not applied, the paper P is pre-dried by the treatment liquid drying unit 130, so that the heat conduction from the peripheral surface 142A to the paper P is suppressed, the fluidity of the ink is lowered, and uneven drying is suppressed. be able to. Further, adding a new temperature control mechanism for preheating is not cost-effective, but according to this image recording method, the processing liquid drying section 130 also serves as a preheating mechanism, thereby reducing costs. can.

<Relationship between temperature difference between guide surface and paper and visibility of drying unevenness>
It was confirmed that drying unevenness can be reduced by preheating the paper P to relatively reduce the temperature difference between the peripheral surface 142A of the image forming drum 142 and the paper P.

FIG. 13 shows the relationship between the temperature difference (T _G −T _P ) between the temperature T _G of the peripheral surface 142A of the image forming drum 142 of the inkjet recording apparatus 100 and the temperature T _P of the paper P, and the visibility of drying unevenness. graph. In FIG. 13, the horizontal axis indicates the temperature difference (T _G −T _P ), and the vertical axis indicates the sensory evaluation result of the visibility level of drying unevenness of a solid image formed at each temperature difference.

The temperature T _G of the peripheral surface 142A of the image forming drum 142 and the temperature T _P of the paper P are measured at positions immediately before ink droplets are ejected by the inkjet head 146C, the inkjet head 146M, the inkjet head 146Y, and the inkjet head 146K. bottom. Here, the temperature _TG of the peripheral surface 142A of the image forming drum 142 was 26-32.degree. In addition, the temperature of the ink is 30°C.

The sensory evaluation results of the visibility level of drying unevenness were classified as follows. Classification A or higher is acceptable.

A ⁺⁺ : Very good (no uneven drying visible)
A ⁺ : Worse than A ⁺⁺ and better than A A: Good (drying unevenness is hardly visible)
B ⁺ : Worse than A and better than B B: Poor (uneven drying is slightly visible)
C ⁺ : Worse than B and better than C C: Very bad (uneven drying is visible)
The visibility of drying unevenness of a solid image formed at each temperature difference is plotted in the graph of FIG. The straight line shown in FIG. 13 is an approximate straight line derived from each plotted point.

As shown in FIG. 13, in order to make the visibility of drying unevenness of a solid image equal to or higher than the pass line, the temperature _TG of the guide surface when the ink lands on the paper P and the temperature TP of the paper _P must be It can be seen that it is preferable to have a relationship of 0≦T _G −T _P ≦1.2 [° C.], and it is more preferable to have a relationship of 0≦T _G −T _P ≦1.0 [° C.].

Note that the amount of heating required in the treatment liquid drying section 130 changes depending on the type of paper P, such as the material and thickness. Therefore, it is preferable to provide a reference table in which the type of paper P and the amount of heating (for example, the temperature of the drying air) are linked, and control the heating amount of the treatment liquid drying section 130 according to the type of paper P. . Further, the required amount of heating changes depending on whether or not the treatment liquid is applied. Therefore, it is preferable to provide a reference table in which the presence or absence of application of the treatment liquid and the amount of heating are linked, and control the amount of heating of the treatment liquid drying section 130 according to the presence or absence of application of the treatment liquid.

<Others>
So far, the case where the temperature of the peripheral surface 142A of the image forming drum 142 is higher than the temperature of the paper P has been described. On the other hand, when the temperature of the paper P is higher than the temperature of the peripheral surface 142A of the image forming drum 142, in order to make the visibility of the drying unevenness of the solid image higher than the pass line, based on the knowledge so far, -1.2 ≤ T _G - T _P ≤ 0 [°C], and more preferably -1.0 ≤ T _G - T _P ≤ 0 [°C]. . When these are integrated, in order to make the visibility of drying unevenness of a solid image higher than the acceptable line, it is preferable to have a relationship of |T _G −T _P |≦1.2 [° C.], and |T _G −T It is more preferable to have a relationship of _P |≦1.0 [° C.].

Equipped with a temperature sensor (not shown) that measures the temperature of the paper P conveyed by the image forming drum, the treatment liquid drying control unit 264 measures the temperature of the paper P with the temperature sensor (an example of the “temperature measurement step”), The processing liquid drying section 130 may be feedback-controlled based on the measurement result of the temperature sensor. In this case, the treatment liquid drying control section 264 may set the temperature of the drying air according to the measurement result of the temperature sensor. A temperature sensor (not shown) that measures the temperature of the peripheral surface 142A of the image forming drum 142 is provided. The liquid drying section 130 may be feedback-controlled.

In the present embodiment, the guide surface supporting the paper P is the peripheral surface 142A of the image forming drum 142, which is a curved surface. may have at least one of a number of protrusions and a number of holes.

In this embodiment, the recording medium is a sheet of paper P, but the recording medium is not limited to paper, and various sheet bodies such as resin sheets, films, and other materials and shapes can be used.

In this embodiment, the recording medium is preheated to establish the relationship of 0≦T _G −T _P ≦1.2 [° _C. ]. A relationship of _P ≤ 1.2 [°C] may be established.

The technical scope of the present invention is not limited to the scope described in the above embodiments. Configurations and the like in each embodiment can be appropriately combined between each embodiment without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10... Guide surface 12... Convex part 14... Hole part 20... Guide surface 22... Hole part 100... Inkjet recording device 109... Conveyance part 110... Paper feed part 112... Paper feed device 112A... Paper feed tray 114... Feeder board 116... Feed drum 120 Treatment liquid application unit 122 Treatment liquid application drum 123 Gripper 124 Treatment liquid application device 130 Treatment liquid drying unit 132 Treatment liquid drying drum 133 Gripper 134 Warm air blower 135 Warm air blower 136 Hot air blower 140 Image forming unit 142 Image forming drum 142A Peripheral surface 143 Gripper 144 Head unit 146 Inkjet head 146C Inkjet head 146K Inkjet head 146M Inkjet head 146Y Inkjet head 148 Nozzle surface 148 -i Nozzle surface 150 Head module 150-i Head module 152 Support frame 154 Cable 156 Dummy plate 156A Surface 158-i Nozzle arrangement portion 160 Nozzle row 162 Nozzle 164 Ejector 166 Pressure chamber 168 Piezoelectric element 170 Nozzle channel 172 Individual supply channel 174 Supply side common branch channel 176 Vibration plate 178 Individual electrode 180 Piezoelectric body 182 Cover plate 184 Movable space 190 Scanner 200 Ink drying unit 210 Chain delivery 212 Chain 214 Gripper 220 Paper guide 222 First paper guide 224 Second paper guide 230 Warm air blower 232 Paper detection sensor 240 Stacking unit 242 Stacking device 244 Stacking tray 250 System Controller 252 Communication unit 254 Host computer 256 Image memory 258 Conveyance control unit 260 Paper feed control unit 262 Treatment liquid application control unit 264 Treatment liquid drying control unit 266 Image formation control unit 268 Ink drying control unit 270 integration control unit 272 operation unit 274 display unit 276 parameter storage unit 278 program storage unit 280 sensor

Claims (11)

a conveying step of supporting a recording medium on a guide surface and conveying the recording medium integrally with the guide surface;
an image forming step of forming an image by ejecting liquid from a liquid ejection head onto the conveyed recording medium;
a preheating step of preheating the recording medium prior to the image forming step;
with
Assuming that the temperature of the guide surface in the image forming step is T _G and the temperature of the recording medium is T _P ,
0≦T _G −T _P ≦1.2 [° C.]
An image recording method having the relationship of 0≦T _G −T _P ≦1.0 [° C.]
2. The image recording method according to claim 1, wherein the relationship is: the temperature of the recording medium is the temperature of the recording medium at a position where the liquid is applied;
3. The image recording method according to claim 1, wherein the temperature of the guide surface is the temperature of the guide surface at a position integral with a position of the recording medium to which the liquid is applied. a treatment liquid applying step of applying a treatment liquid to the recording medium before the image forming step;
a switching step of switching presence/absence of the treatment liquid coating step;
a treatment liquid drying step for heating the recording medium coated with the treatment liquid when the treatment liquid application step is performed, the treatment liquid also serving as the preheating step regardless of whether or not the treatment liquid application step is performed. a drying process;
The image recording method according to any one of claims 1 to 3, comprising: 5. The image recording method according to any one of claims 1 to 4, wherein the guide surface has at least one of projections and holes. 6. The image recording method according to any one of claims 1 to 5, wherein in the conveying step, the recording medium is supported using a peripheral surface of a drum that rotates about an axis as the guide surface. 7. The image recording method according to claim 1, further comprising a liquid drying step of drying the liquid after the image forming step. A temperature measurement step of measuring the temperature of the recording medium,
8. The image recording method according to claim 1, wherein the preheating step preheats the recording medium based on the measured temperature. a transport mechanism that supports a recording medium on a guide surface and transports the recording medium integrally with the guide surface;
a liquid ejection head that ejects liquid onto the transported recording medium to record an image;
a preheating mechanism for preheating the recording medium before recording the image;
with
Let T _G be the temperature of the guide surface when recording the image, and T _P be the temperature of the recording medium.
0≦T _G −T _P ≦1.2 [° C.]
An image recording device having a relationship of 10. An image recording apparatus according to claim 9, wherein said preheating mechanism includes a fan for supplying dry air to said recording medium. 11. The image recording apparatus according to claim 9, further comprising a drying mechanism for drying the ejected liquid.

Images