JP2021102299A - Image forming apparatus - Google Patents

Abstract

To provide an image formation apparatus that is able to form a high-quality image regardless of a surface state of a recording medium.SOLUTION: An image formation apparatus 10 has: an intermediate transfer body 210; a precoat layer formation unit 220 for forming a precoat layer by applying a precoat liquid onto the intermediate transfer body; an ink application unit 230 for applying ink onto the precoat layer; and a transfer unit 260 for transferring the ink to a recording medium. The precoat layer formation unit changes the thickness of the precoat layer according to a surface shape of the recording medium.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus.

The transfer-type inkjet image forming apparatus applies ink to the surface of the intermediate transfer body to form an intermediate image, and transfers the intermediate image from the intermediate transfer body to a recording medium to form an image. Since the transfer type inkjet method can produce an image easily and inexpensively, it is adopted in various printing fields including special printing such as various printing, marking, fine line formation, and color filter.

On the other hand, in the transfer type inkjet method, when the intermediate image formed on the surface of the intermediate transfer body is transferred, the recording medium and the ink are pressed in contact with each other, so that the transferability is lowered depending on the surface condition of the recording medium. , It may not be possible to obtain an image having the desired image quality. Therefore, an image forming apparatus capable of supporting various recording media has been studied.

For example, in Patent Document 1, as a means for adjusting the thickness of the image of the surface layer of the intermediate transfer body before being transferred to the recording surface of the recording medium according to the surface roughness of the recording surface of the recording medium. An image forming apparatus including an ink density adjusting apparatus is described. According to Patent Document 1, by providing the adjustment device, even if an image is formed on a recording medium, a high-quality image can be formed on the recording surface of the recording medium regardless of the surface roughness of the recording medium. There is.

Japanese Unexamined Patent Publication No. 2014-148160

As a result of examination by the present inventor, as in Patent Document 1, transferability is improved by adjusting the amount of ink ejected according to the size of the unevenness (arithmetic mean roughness Ra) on the surface of the recording medium. be able to. On the other hand, the ink adhering to the surface (convex portion) of the recording medium is easily crushed, and therefore image unevenness is likely to occur. On the other hand, if the transfer pressure is lowered in order to prevent the ink adhering to the surface (convex portion) of the recording medium from being crushed, it becomes difficult for the surface (concave portion) of the recording medium to come into contact with the ink, and the transferability is lowered. Cheap.

The present invention has been made in view of this point, and an object of the present invention is to provide an image forming apparatus capable of forming a high-quality image regardless of the surface condition of a recording medium.

The image forming apparatus of the present invention includes an intermediate transfer body, a precoat layer forming portion for applying a precoat liquid on the intermediate transfer body to form a precoat layer, and an ink for applying ink on the precoat layer. It has an applying portion and a transfer portion for transferring the ink to a recording medium, and the precoat layer forming portion changes the thickness of the formed precoat layer according to the surface shape of the recording medium. ..

According to the present invention, it is possible to provide an image forming apparatus capable of forming a high quality image regardless of the surface condition of the recording medium.

FIG. 1 is a schematic view showing a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram showing a main part of a control system of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a flowchart showing an example of an operation example when performing image formation control in the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic view showing the configuration of the image forming apparatus according to the second embodiment of the present invention. FIG. 5 is a flowchart showing an example of an operation example when performing image formation control in the image forming apparatus according to the second and third embodiments of the present invention. FIG. 6 is a schematic view showing the configuration of the image forming apparatus according to the third embodiment of the present invention. FIG. 7 is a flowchart showing an example of an operation example when performing image formation control in the image forming apparatus according to the fourth embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following forms.

[First Embodiment]
FIG. 1 is a schematic view showing an exemplary configuration of an image forming apparatus 10 according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a main part of the control system of the image forming apparatus 10 according to the embodiment of the present invention.

First, a main apparatus configuration in the image forming apparatus 10 will be described mainly with reference to FIG. The image forming apparatus 10 includes a paper feeding unit 100, an image forming unit 200, and a paper ejection unit 300.

The paper feed unit 100 includes a paper feed tray 110 for storing the recording medium P, a medium supply unit 120 for transporting and supplying the recording medium P from the paper feed tray 110 to the image forming unit 200, and the surface roughness of the recording medium P. A surface roughness measuring unit 130 for measuring the above is provided.

The medium supply unit 120 includes a ring-shaped belt whose inside is supported by two rollers, and the recording medium P is moved from the paper feed tray 110 by rotating the rollers with the recording medium P placed on the belts. It is conveyed to the image forming unit 200.

The surface roughness measuring unit 130 measures the surface roughness (arithmetic mean roughness (Ra) and maximum height (Rz)) of the surface on which the image is formed on the recording medium P before being conveyed to the image forming unit 200. Measure.

The surface roughness measuring unit 130 is a known roughness measuring device, and measures the surface roughness of the recording medium P (paper). The surface roughness measuring unit 130 can measure the surface roughness using, for example, a laser microscope VK8700 manufactured by KEYENCE CORPORATION. In the first embodiment, the surface roughness measuring unit 130 measures both the arithmetic mean roughness (Ra) and the maximum height (Rz) of the recording medium P.

The image forming unit 200 forms a precoat layer on the intermediate transfer body 210, which is an endless belt, three support rollers 211, 212, and 213 for rotatably stretching the intermediate transfer body 210, and the intermediate transfer body 210. Precoat layer forming section 220 for feeding, an ink applying section 230 for applying ink to the precoat layer formed on the surface of the intermediate transfer body 210, and a recording medium transport section 240 for transporting the recording medium P. A transfer unit 250 that transfers the recording medium P conveyed from the paper unit 100 to the recording medium transfer unit 240, a transfer unit 260 for transferring ink to the transferred recording medium P, and transfer from the recording medium transfer unit 240. It includes a delivery unit 270 that sends the recorded recording medium P to the paper ejection unit 300.

Further, the image forming apparatus 10 includes a fixing unit 280 that irradiates the ink transferred to the recording medium P with active rays to cure the ink, and a cleaning unit 290 that cleans the surface of the intermediate transfer body 210. ..

The intermediate transfer body 210 is arranged on, for example, a base material layer made of a resin material such as polyimide, an elastic layer made of silicon rubber or the like arranged on the surface of the base material layer, and the surface of the elastic layer. It has a surface layer made of a material having high chemical resistance such as fluororesin. As described above, the intermediate transfer body 210 has a layer structure of at least two or more layers including an elastic layer and a surface layer made of a material having high chemical resistance, so that the intermediate transfer body 210 maintains chemical resistance, wettability, and the like. Has strength and elasticity.

The intermediate transfer body 210 is composed of an endless belt, and is stretched in an inverted triangular shape on three support rollers 211, 212, and 213. The portions of the intermediate transfer body 210 stretched over the three support rollers 211, 212, and 213 located at the left and right apex portions of the inverted triangle shape are the landing surfaces of the ink applied from the ink application unit 230. .. The support roller 213 located at the lower apex portion of the inverted triangular shape of the intermediate transfer body 210 is a pressure roller that pressurizes the intermediate transfer body 210 toward the recording medium transport portion 240 by a predetermined nip pressure, and is an ink. It functions as a pressurizing unit that transfers the intermediate image formed by applying the ink ejected from the applying unit 230 to the recording medium P.

Of the three support rollers 211, 212 and 213, at least one roller is a drive roller and is driven under the control of the control unit 20. As a result, the intermediate transfer body 210 rotates in the A direction (clockwise direction in FIG. 1).

The precoat layer forming portion 220 includes a roll coater 221 and a scraper 222. In the precoat layer forming portion 220, the roll coater 221 applies the precoat liquid to the surface of the intermediate transfer body 210, and the scraper 222 removes an excess amount of the precoat liquid to smooth the surface of the applied precoat liquid. In the precoat layer forming portion 220, a method using a bar coater, an inkjet method, or the like may be used.

Further, as the precoat liquid, liquid components such as water and a water-soluble organic solvent can be used. The precoat liquid may contain an adjusting agent for adjusting the surface tension and the viscosity.

In the ink application unit 230, under the control of the control unit 20, active ray-curable compositions (ink for inkjet) of each color of Y (yellow), M (magenta), C (cyan), and K (black) are intermediately transferred. An intermediate image is formed by applying the nozzle opening provided on the ink ejection surface facing the body 210 onto the precoat layer formed on the surface of the intermediate transfer body 210.

In the image forming apparatus 10 of the present embodiment, four inkjet heads 230Y, 230M, 230C and 230K corresponding to four color inks of yellow (Y), magenta (M), cyan (C) and black (K) are used. The intermediate transfer members 210 are arranged so as to be arranged at predetermined intervals in the order of Y, M, C, and K colors from the upstream side in the rotation direction (movement direction).

The ink applying unit 230 includes the above four inkjet heads. Each inkjet head is provided with a pressure chamber for storing ink, a piezoelectric element provided on the wall surface of the pressure chamber, and a plurality of recording elements each having a nozzle. When a drive signal that deforms the piezoelectric element is input to this recording element, the pressure chamber is deformed due to the deformation of the piezoelectric element, the pressure in the pressure chamber changes, and ink droplets are ejected from a nozzle communicating with the pressure chamber. To do.

The arrangement range of the nozzles included in the inkjet head in the orthogonal direction covers the width of the recording medium P conveyed by the recording medium conveying unit 240 in the orthogonal direction of the region where the image is formed. The ink application unit 230 is used with its position fixed with respect to the rotation axis of the recording medium transport unit 240 when the intermediate image is formed. That is, the image forming apparatus 10 is a single-pass type inkjet image forming apparatus.

In the present embodiment, as the ink discharged from the ink applying portion 230 to the intermediate transfer body 210, an ink having an active ray curability that is cured by being irradiated with active rays (for example, ultraviolet rays), more specifically, ultraviolet rays (for example, ultraviolet rays) An active ray-curable ink whose viscosity changes according to the amount of light of UV: ultraviolet) is used. That is, the image forming portion of the image forming apparatus 10 adopts a UV curable inkjet method.

The recording medium transport unit 240 is composed of, for example, a metal drum, and transports the intermediate image to the recording medium P to be transferred. The recording medium transport section 240 is arranged in contact with a part of the surface of the intermediate transfer body 210, and the transfer section 260 is formed by pressurizing the contacting surface of the intermediate transfer body 210 by the support roller 213. The recording medium transport unit 240 may have a claw (not shown) for fixing the tip of the recording medium P. Under the control of the control unit 20, the recording medium transport unit 240 transports the recording medium P to the transfer unit 260 by fixing the tip of the recording medium P to the claw and rotating it in the counterclockwise direction in FIG. ..

The delivery unit 250 delivers the recording medium P conveyed by the medium supply unit 120 of the paper feed unit 100 to the recording medium transfer unit 240. The delivery unit 250 is provided at a position between the medium supply unit 120 and the recording medium transfer unit 240 of the paper feed unit 100, and one end of the recording medium P conveyed from the medium supply unit 120 is held by the swing arm unit 251. It is picked up and delivered to the recording medium transport unit 240 via the delivery drum 252.

The transfer unit 260 is a pressure unit composed of a support roller 213 as a pressure roller and a recording medium transfer unit 240 arranged with the intermediate transfer body 210 interposed therebetween, and transfers the intermediate transfer body 210 to the recording medium. By pressurizing the recording medium P conveyed to the unit 240 with a predetermined nip pressure, the intermediate image formed on the surface of the intermediate transfer body 210 is transferred to the surface of the recording medium P.

The delivery unit 270 includes a belt loop 272 having a ring-shaped belt whose inside is supported by two rollers, and a cylindrical transfer drum 271 that transfers the recording medium P from the recording medium transport unit 240 to the belt loop 272. .. The recording medium P delivered onto the belt loop 272 from the recording medium transport section 240 by the delivery drum 271 is conveyed by the belt loop 272 and sent to the paper ejection section 300.

The fixing unit 280 is arranged on the downstream side of the transfer unit 260 in the transport direction of the recording medium P by the recording medium transport unit 240, and under the control of the control unit 20, the active line (active line) toward the surface of the recording medium transport unit 240. For example, ultraviolet rays) are irradiated. As a result, the inks constituting the intermediate image are cured (mainly cured).

The cleaning unit 290 is a cleaning roller such as a web roller or a sponge roller, and comes into contact with the surface of the intermediate transfer body 210 on the downstream side of the transfer unit 260. The cleaning unit 290 is driven and rotated by the cleaning roller under the control of the control unit 20, so that the residual composition (residual coating) remaining on the surface of the intermediate transfer body 210 without being transferred to the recording medium P by the transfer unit 260. Thing) is removed.

The paper ejection unit 300 has a plate-shaped paper ejection tray 310 on which the recording medium P sent out from the image forming unit 200 by the delivery unit 270 is placed.

Next, other main functional configurations in the image forming apparatus 10 will be described mainly with reference to FIG. The image forming apparatus 10 includes a precoat layer forming unit 220, an ink applying unit 230, a surface roughness measuring unit 130, a control unit 20, and an input / output interface 30.

The control unit 20 includes a CPU 21 (Central Processing Unit), a RAM 22 (Random Access Memory), a ROM 23 (Read Only Memory), and a storage unit 24.

The CPU 21 reads various control programs (for example, an image formation condition changing program) and setting data stored in the ROM 23 and stores them in the RAM 22, and executes the programs to perform various arithmetic processes. In addition, the CPU 21 comprehensively controls the overall operation of the image forming apparatus 10.

The RAM 22 provides the CPU 21 with a working memory space and stores temporary data. The RAM 22 may include a non-volatile memory.

The ROM 23 stores various control programs, setting data, and the like executed by the CPU 21. Instead of the ROM 23, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

A print job (specifically, an image formation instruction including various user setting information such as the number of prints) input from the external device 40 via the input / output interface 30 and an image related to the print job are stored in the storage unit 24. Data is stored. As the storage unit 24, for example, an HDD (Hard Disk Drive) may be used, or a DRAM (Dynamic Random Access Memory) or the like may be used in combination.

The input / output interface 30 operates as an input receiving unit and an output unit, is connected to the input / output interface of the external device 40, and mediates the transmission and reception of data between the external device 40 and the control unit 20. The input / output interface 30 is composed of, for example, any of various serial interfaces, various parallel interfaces, or a combination thereof.

In the image forming apparatus 10 according to the first embodiment, the thickness of the precoat layer is increased by the precoat layer forming unit 220 under the control of the control unit 20 according to the surface shape of the surface on which the image of the recording medium P is formed. It is characterized by changing.

When the maximum height (Rz) of the surface of the recording medium P is larger, the precoat layer forming portion 220 makes the thickness of the precoat layer thicker. When the maximum height (Rz) of the surface of the recording medium P is larger and the unevenness difference of the surface is larger, it is difficult for the intermediate transfer body 210 to follow the surface shape of the recording medium P, and the transfer unit 260 Since it is also difficult to uniformly pressurize the surface of the recording medium P, the intermediate image may not be sufficiently transferred to the surface of the recording medium P. On the other hand, in the image forming apparatus 10 according to the first embodiment, when the difference in surface irregularities is large, the thickness of the precoat layer is increased to further increase the elasticity of the precoat layer. Thereby, the transferability of the ink to the recording medium P can be improved regardless of the surface shape (unevenness) of the surface of the recording medium P. Further, at this time, since the ink can be transferred to the recording medium P without increasing the amount of ink or increasing the pressure at the time of transfer by the transfer unit 260, the ink is less likely to be crushed.

On the other hand, when the maximum height (Rz) of the surface of the recording medium P is smaller, the precoat layer forming portion 220 makes the thickness of the precoat layer thinner. When the maximum height (Rz) of the surface of the recording medium is small, even if a small amount of precoat liquid is applied, the intermediate transfer body and the surface of the recording medium are brought into contact with each other to transfer the ink to the recording medium. Can be done.

In this way, by applying an appropriate amount of the precoat liquid to the surface of the recording medium P according to the measurement result of the surface roughness measuring unit 130, the transfer rate is high and the transfer rate is high regardless of the surface shape of the recording medium P. Images with less ink crushing can be transferred.

Further, when the maximum height (Rz) of the surface of the recording medium P is less than a predetermined value and the thickness of the precoat layer is made thinner, the transfer unit 260 further increases the arithmetic mean roughness (Ra) of the recording medium P. When is greater than or equal to a predetermined value, the pressure at the time of transferring the ink to the recording medium is set to a higher pressure. Even when the difference in unevenness on the surface of the recording medium P is not so large, when the surface roughness is coarser, it is also difficult for the transfer unit 260 to uniformly pressurize the surface of the recording medium P, so that an intermediate image is recorded. It may not be sufficiently transferred to the surface of the medium P. In such a case, by increasing the pressure at the time of transfer, the adhesion between the recording medium and the ink can be improved, so that the transferability of the ink to the recording medium can be improved.

On the other hand, when the arithmetic mean roughness (Ra) of the surface of the recording medium P is less than a predetermined value, the transfer unit 260 sets the pressure at the time of transfer to a smaller pressure. When the arithmetic mean roughness (Ra) of the recording medium is less than a predetermined value, the precoat layer is formed so as to be thicker, and therefore, the ink at the time of transfer is formed by lowering the pressure. Can be suppressed from being crushed. Further, since the precoat layer is formed thickly, the surface state of the recording medium does not affect the transfer, so that an image having high transferability can be obtained even at a smaller pressure. At this time, since the ink can be transferred to the recording medium P without increasing the amount of ink, the ink is less likely to be crushed.

In the image forming apparatus 10 according to the first embodiment, the surface roughness measuring unit 130 measures the maximum height (Rz) and the arithmetic mean roughness (Ra) of the recording medium P under the control of the control unit 20. .. Based on this measurement result, it is decided whether to change the thickness of the precoat layer or the pressure during transfer. As a result, the thickness of the precoat layer or the pressure at the time of transfer, which is suitable for the recording medium actually used, can be optimized, so that a high-quality image can be obtained.

Next, an operation example when executing the image formation control in the image forming apparatus 10 according to the first embodiment will be described. FIG. 3 is a flowchart showing an example of an operation when executing image formation control in the image forming apparatus 10 according to the first embodiment. In the process of FIG. 3, the image forming apparatus 10 performs a print job from the operator, which includes image data indicating an image to be formed and recording medium data indicating selection or setting of a recording medium to form an image. This is executed when the data is received via the input / output interface 30.

The control unit 20 causes the surface roughness measuring unit 130 to measure the maximum height (Rz) and the arithmetic mean roughness (Ra) of the surface of the recording medium P (S10).

Next, the control unit 20 determines whether the value of the maximum height (Rz) of the surface of the recording medium P measured by the surface roughness measuring unit 130 and stored in the storage unit 24 is equal to or higher than a predetermined value ( S11), the thickness of the precoat layer is determined.

At this time, if the control unit 20 determines that the maximum height (Rz) value of the surface of the recording medium P measured by the surface roughness measuring unit 130 is equal to or higher than a predetermined value (S11, YES), the precoating unit 20 is used. The thickness of the precoat layer to be formed on the layer forming portion 220 is determined to be a thicker first thickness (S12).

On the other hand, when the control unit 20 determines that the maximum height (Rz) of the surface of the recording medium P measured by the surface roughness measuring unit 130 is less than a predetermined value (S11, NO), the precoat layer forming unit The thickness of the precoat layer to be formed in 220 is determined to be a thinner second thickness (S12'). The second thickness can be the normal thickness of the precoat layer, and the first thickness can be thicker than the second thickness.

When the thickness of the precoat layer is determined to be the second thickness, the control unit 20 measures the surface roughness measurement unit 130, and the arithmetic mean roughness (Ra) of the surface of the recording medium P stored in the storage unit 24. ) Is equal to or greater than a predetermined value (S13). Then, when the control unit 20 determines that the value of the arithmetic mean roughness (Ra) is equal to or higher than a predetermined value (S13, YES), the control unit 20 sets the pressure at the time of transfer by the transfer unit 260 to a higher first pressure. (S14). On the other hand, when the control unit 20 determines that the value of the arithmetic mean roughness (Ra) is less than a predetermined value (S13, NO), the pressure at the time of transfer by the transfer unit 260 is set to a smaller second pressure. (S14'). The second pressure can be a normal pressure at the time of transfer, and the first pressure can be a pressure higher than the second pressure.

When the thickness of the precoat layer is determined to be the first thickness, the control unit 20 determines the pressure at the time of transfer by the transfer unit 260 to be a smaller second pressure (S14').

Then, the control unit 20 causes the precoat layer forming unit 220 to form the precoat layer on the surface of the intermediate transfer body 210 with the determined thickness of the precoat layer (S15).

Next, the control unit 20 causes the ink application unit 230 to apply ink to the surface of the intermediate transfer body 210 so as to obtain a transmitted image to form an intermediate image (S16).

Next, the control unit 20 transfers the intermediate image formed on the surface of the intermediate transfer body 210 to the transfer unit 260, and the transfer unit 260 applies the first pressure or the second pressure determined in the previous step. , Transferred to the recording medium P (S17).

The control unit 20 moves the recording medium P on which the ink is transferred to the fixing unit 280. Next, the control unit 20 irradiates the fixing unit 280 with active rays (for example, ultraviolet rays) on the surface on which the ink of the recording medium P is transferred, and fixes the ink on the recording medium P (S18). As a result, this control ends.

According to this embodiment, a high quality image can be formed regardless of the surface condition of the recording medium.

[Second Embodiment]
FIG. 4 is a schematic view showing an exemplary configuration of the image forming apparatus 11 according to the second embodiment of the present invention.

The image forming apparatus 11 according to the second embodiment is an image forming apparatus according to the first embodiment only in that it has an image observing unit 400 for observing the transferred image transferred to the surface of the recording medium after transfer. Different from 10. Therefore, the same components as those of the image forming apparatus 10 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The image observation unit 400 can be a known image sensor or the like that can optically capture the transferred image. Based on the image of the transferred image observed by the image observing unit 400, the control unit 20 determines the transfer rate of the transferred image (the ratio of the amount of ink constituting the transferred image to the amount of ink applied by the ink applying unit 230). By calculation, the image observation unit 400 and the control unit 20 operate as the image quality detection unit in the second embodiment.

In the image forming apparatus 11 according to the second embodiment, the precoat layer forming unit 220 of the control unit 20 determines the image quality of the transferred image (transfer rate of the image transferred to the recording medium) detected by the image quality detecting unit. Under control, the thickness of the precoat layer is changed. Further, the transfer unit 260 is characterized in that the transfer pressure at the time of transfer is changed under the control of the control unit 20.

The image observation unit 400 is arranged on the downstream side of the fixing unit 280, and detects the transferred image transferred to the surface of the recording medium P after transfer. The control unit 20 obtains the transfer rate of the transferred image based on the image quality of the image observed by the image observation unit 400.

The precoat layer forming unit 220 changes the thickness of the precoat layer according to the transfer rate of the transferred image detected by the image observation unit 400. That is, when the transfer rate is lower (less than the first predetermined value), it is presumed that the difference in unevenness on the surface of the recording medium P is large (Rz is large), so that the thickness of the precoat layer is increased. By making the ink thicker, the transfer rate of the ink can be further increased. On the other hand, when the transfer rate is higher (when it is equal to or higher than the first predetermined value), it is presumed that the difference in unevenness on the surface of the recording medium P is small (Rz is small), so that the thickness of the precoat layer is increased. Even if it is made thinner, the transfer rate of the ink can be sufficient.

Further, in the transfer unit 260, when the transfer rate is lower (less than the first predetermined value) and the thickness of the precoat layer is made thinner, and when the transfer rate is lower (less than the second predetermined value). When), the surface roughness of the recording medium P is presumed to be rougher, so that the pressure at the time of transferring the ink to the recording medium is set to a higher pressure.

The image forming apparatus 11 according to the second embodiment changes the thickness of the precoat layer based on the transfer rate of the image quality (intermediate image transferred to the recording medium) detected by the image observing unit 400. Or decide whether to change the pressure during transfer. As a result, the thickness of the precoat layer or the pressure at the time of transfer, which is suitable for the recording medium actually used, can be optimized, so that a high quality image can be obtained.

In the second embodiment, "less than the first predetermined value" means that the transfer rate of the image transferred by the transfer unit is less than 80%, and "less than the second predetermined value" means the transfer unit. Means that the transfer rate of the transferred image is less than 90%.

Next, an operation example when executing the image formation control in the image forming apparatus 11 according to the second embodiment will be described. FIG. 5 is a flowchart showing an example of an operation when executing image formation control in the image forming apparatus 11 according to the second embodiment.

The control unit 20 causes the image observation unit 400 to detect the transferred image transferred to the surface of the recording medium P. Then, the transfer rate of the transferred image detected by the image observation unit 400 is calculated (S20).

Next, the control unit 20 determines whether the calculated transfer rate of the transferred image is less than the first predetermined value (S21), and determines the thickness of the precoat layer.

At this time, if the control unit 20 determines that the calculated transfer rate of the transferred image is less than the first predetermined value (S21, YES), the thickness of the precoat layer to be formed on the precoat layer forming unit 220. The thickness is determined to be a thicker first thickness (S22).

On the other hand, when the control unit 20 determines that the calculated transfer rate of the transferred image is equal to or higher than the first predetermined value (S21, NO), the thickness of the precoat layer to be formed in the precoat layer forming unit 220. Is determined to be a thinner second thickness (S22'). The second thickness can be the normal thickness of the precoat layer, and the first thickness can be thicker than the second thickness.

When the thickness of the precoat layer is determined to be the second thickness, the control unit 20 determines whether the transfer rate of the displayed transferred image is less than the second predetermined value (S23). Then, when the control unit 20 determines that the transfer rate of the transferred image is less than the second predetermined value (S23, YES), the control unit 20 changes the pressure at the time of transfer by the transfer unit 260 to a larger first pressure. Determine (S24). On the other hand, when the control unit 20 determines that the transfer rate of the transferred image is equal to or higher than the second predetermined value (S23, NO), the pressure at the time of transfer by the transfer unit 260 is reduced to a smaller second pressure. Determine (S24'). The second pressure can be a normal pressure at the time of transfer, and the first pressure can be a pressure higher than the second pressure.

Then, the control unit 20 causes the precoat layer forming unit 220 to form the precoat layer on the surface of the intermediate transfer body 210 with the determined thickness of the precoat layer (S25).

Next, the control unit 20 causes the ink application unit 230 to apply ink to the surface of the intermediate transfer body 210 so as to form a transmitted image (S26).

Next, the control unit 20 transfers the intermediate image formed on the surface of the intermediate transfer body 210 to the transfer unit 260, and the transfer unit 260 applies the first pressure or the second pressure determined in the previous step. , Transferred to the recording medium P (S27).

The control unit 20 moves the recording medium P on which the ink is transferred to the fixing unit 280. Next, the control unit 20 irradiates the fixing unit 280 with active rays (for example, ultraviolet rays) on the surface on which the ink of the recording medium P is transferred, and fixes the ink on the recording medium P (S28). As a result, this control ends.

According to this embodiment, a high quality image can be formed by determining the thickness of the precoat layer and the pressure at the time of transfer, which are the best than the transfer rate.

[Third Embodiment]
FIG. 6 is a schematic view showing an exemplary configuration of the image forming apparatus 12 according to the third embodiment of the present invention.

The image forming apparatus 12 according to the third embodiment is an image forming apparatus according to the first embodiment only in that it has an image observing unit 500 for detecting the image quality of the residual image remaining on the intermediate transfer body 210 after transfer. Different from 10. Therefore, the same components as those of the image forming apparatus 10 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The image observation unit 500 can be a known image sensor or the like that can optically capture the transferred image. Based on the image of the residual image observed by the image observation unit 500, the control unit 20 transfers the transfer image (transfer obtained from the amount of ink constituting the residual image with respect to the amount of ink applied by the ink application unit 230). By calculating the ratio of the amount of ink constituting the image), the image observation unit 500 and the control unit 20 operate as the image quality detection unit in the third embodiment.

In the image forming apparatus 12 according to the third embodiment, the precoat layer forming unit 220 has a precoat layer forming unit 220 according to the image quality (transfer rate obtained from the residual rate) of the residual image remaining on the intermediate transfer body 210 detected by the image quality detecting unit. Under the control of the control unit 20, the thickness of the precoat layer is changed. Further, the transfer unit 260 is characterized in that the pressure at the time of transfer is changed under the control of the control unit 20.

The image observation unit 500 is arranged between the fixing unit 280 and the cleaning unit 290, and detects the image quality of the residual image remaining on the intermediate transfer body 210 after transfer. The control unit 20 determines the transfer rate of the image transferred by the transfer unit 260 (the image transferred to the recording medium) based on the image quality of the residual image remaining on the intermediate transfer body 210 after the transfer.

The precoat layer forming unit 220 changes the thickness of the precoat layer according to the image quality of the residual image remaining on the intermediate transfer body 210 after transfer detected by the image observation unit 500. Determining the thickness and transfer pressure of the precoat layer based on the transfer rate is the same as in the second embodiment, and thus detailed description thereof will be omitted.

According to this embodiment, a high quality image can be formed by determining the thickness of the precoat layer and the pressure at the time of transfer, which are the best than the transfer rate.

[Fourth Embodiment]
The image forming apparatus (not shown) according to the fourth embodiment is used for image forming according to the first embodiment only in that the precoat layer forming unit 220 operates according to the type of recording medium input or selected by the user. Different from device 10. Therefore, the image forming apparatus according to the fourth embodiment will be described with reference to FIGS. 1 and 2.

The image forming apparatus according to the fourth embodiment is characterized in that the control unit 20 refers to the storage unit 24 and determines the thickness of the corresponding precoat layer and the pressure at the time of transfer according to the instruction of the print job. ..

In the fourth embodiment, the storage unit 24 stores in a table the correspondence between the type of recording medium and the thickness and transfer pressure of the precoat layer to be set when forming an image on the recording medium. There is. In this correspondence relationship, the thickness of the precoat layer and the transfer pressure are determined according to the surface shape of the recording medium. Specifically, as in the first embodiment, when the maximum height (Rz) of the surface of the recording medium P is larger, the thickness of the precoat layer is made thicker, and the maximum height of the surface of the recording medium P is increased. When (Rz) is smaller, the thickness of the precoat layer is made thinner. However, when the maximum height (Rz) of the surface of the recording medium P is smaller and the arithmetic mean roughness (Ra) of the recording medium P is equal to or more than a predetermined value, the pressure at the time of transfer should be made higher. In addition, these correspondences have been determined.

An operation example when executing image formation control in the image forming apparatus (not shown) according to the fourth embodiment will be described. FIG. 7 is a flowchart showing an example of an operation when executing image formation control in the image forming apparatus according to the fourth embodiment.

The control unit 20 refers to the storage unit 24 to determine the thickness of the precoat layer corresponding to the recording medium indicated by the recording medium data included in the print job (S31). Further, the control unit 20 refers to the storage unit 24 to determine the pressure at the time of transfer corresponding to the recording medium indicated by the recording medium data included in the print job (S32).

Then, the control unit 20 causes the precoat layer forming unit 220 to form the precoat layer on the surface of the intermediate transfer body 210 with the determined thickness of the precoat layer (S33).

Next, the control unit 20 causes the ink application unit 230 to apply ink to the surface of the intermediate transfer body 210 so as to form a transmitted image (S34).

Next, the control unit 20 causes the transfer unit 260 to transfer to the recording medium P at the determined pressure (S35).

Next, the control unit 20 irradiates the fixing unit 280 with active rays (for example, ultraviolet rays) on the surface on which the ink of the recording medium P is transferred, and fixes the ink on the recording medium P (S36). As a result, this control ends.

According to this embodiment, a high quality image can be formed regardless of the surface condition of the recording medium.

[Fifth Embodiment]
In the first to fourth embodiments, when the input / output interface 30 receives an instruction to change the transfer rate from the user, the control unit 20 sends the precoat layer forming unit 220 to the precoat layer forming unit 220 in response to the instruction from the user. The thickness of the precoat layer to be formed may be changed.

That is, as described above, the transfer rate changes depending on the thickness of the precoat layer. Therefore, when the user who sees the formed image instructs the image forming apparatus to further increase the transfer rate, the control unit 20 forms the precoat layer by making the thickness of the precoat layer thicker the next time the image is formed. The transfer rate of the resulting image may be further increased. Further, when the user instructs the image forming apparatus to reduce the amount of the precoat liquid applied in order to reduce the printing cost, the control unit 20 controls the amount of the precoat liquid applied the next time the image is formed. May be reduced to reduce the cost of printing.

In the first to fifth embodiments, if it is desired to pre-cure the ink on the recording medium P at the time of transfer, an active ray irradiation device (not shown) may be arranged in the transfer unit 260. In that case, the control unit 20 operates the active ray irradiating device in the transfer unit 260 when the active ray irradiating device is provided.

Finally, an evaluation experiment of the image forming apparatus 10 according to the present embodiment will be described. First, an image was formed using the image forming apparatus 10 shown in FIG.

The test image formed on the intermediate transfer body 210 is an image of a magenta color having a liquid volume of 10 pl, a dot ratio of 100%, and a horizontal band of 10% corresponding to the length of the B2 size.

The intermediate transfer material 210 in the experiment of this evaluation has an elasticity composed of a surface layer made of a material having high chemical resistance such as fluororesin, a base layer made of a resin material such as polyimide, and silicon rubber. Has a layer.

Further, among the support rollers 211, 212, and 213 that support the intermediate transfer body 210, the support roller 211 corresponding to the transfer portion 260 is a roller including an elastic layer having a diameter of 100 mm and a rubber thickness of 10 mm.

The fixing portion 280 is an ultraviolet LED light source having a wavelength of 395 nm and an irradiation intensity of 10 W / cm ^2.

The length of the intermediate transfer body 210 and each roller in the axial direction is 800 mm, and the printing speed is 600 mm / s.

Table 1 shows the recording media used in the evaluation experiment.

Images were formed using the recording media shown in Table 1. The results are shown in Table 2.

According to Table 2, when the surface roughness is small like coated paper and woodfree paper, good transferability can be obtained even if the precoat layer is thin, whereas the surface roughness is low like embossed paper. It was found that in the case of a large size, if the precoat layer is thin, good transferability cannot be obtained even if the transfer pressure is increased. On the other hand, it was found that when the surface roughness is large, such as embossed paper, good transferability can be obtained by thickening the precoat layer without increasing the transfer pressure. That is, it was confirmed that by changing the thickness of the precoat layer, a high quality image can be formed regardless of the surface condition of the recording medium.

10, 11, 12 Image forming device 20 Control unit 21 CPU
22 RAM
23 ROM
24 Storage unit 30 Input / output interface 40 External device 100 Paper feed unit 120 Media supply unit 130 Surface roughness measurement unit 200 Image formation unit 210 Intermediate transfer elements 211, 212, 213 Support rollers 220 Precoat layer formation unit 221 Roll coater 222 Scraper 230 Inking section 240 Recording medium transport section 250 Delivery unit 251 Swing arm section 252 Delivery drum 260 Transfer section 270 Delivery section 271 Delivery drum 272 Belt loop 300 Paper discharge section 310 Paper discharge tray 400, 500 Image observation section P Recording medium

Claims (16)

With the intermediate transcript,
A precoat layer forming portion for applying a precoat liquid onto the intermediate transfer body to form a precoat layer, and a precoat layer forming portion.
An ink applying portion for applying ink onto the precoat layer, and an ink applying portion.
A transfer unit for transferring the ink to a recording medium,
Have,
The precoat layer forming portion is an image forming apparatus that changes the thickness of the formed precoat layer according to the surface shape of the recording medium. The image forming apparatus according to claim 1, wherein the precoat layer forming portion changes the thickness of the formed precoat layer according to the surface roughness of the recording medium. The image forming apparatus according to claim 2, wherein the precoat layer forming portion increases the thickness of the formed precoat layer as the surface roughness of the recording medium becomes coarser. The image forming apparatus according to claim 2, wherein the precoat layer forming portion makes the thickness of the formed precoat layer thinner as the surface roughness of the recording medium becomes smoother. The image forming apparatus according to any one of claims 2 to 4, wherein the surface roughness of the recording medium is the arithmetic mean roughness (Ra) or the maximum height (Rz) of the recording medium. The image forming apparatus according to claim 5, wherein the precoat layer forming portion makes the thickness of the formed precoat layer thicker when the arithmetic mean roughness (Ra) of the recording medium is equal to or more than a predetermined value. .. It has a surface roughness measuring unit for measuring the surface roughness of the recording medium, and has a surface roughness measuring unit.
The image forming apparatus according to any one of claims 1 to 6, wherein the precoat layer forming portion changes the thickness of the precoat layer according to the measurement result of the surface roughness measuring portion. The image forming apparatus according to claim 7, wherein the surface roughness measuring unit measures the surface roughness of the recording medium before the recording medium is conveyed. When the maximum height (Rz) of the surface of the recording medium is not more than a predetermined value and the arithmetic mean roughness (Ra) is not more than a predetermined value, the transfer unit transfers the ink to the recording medium. The image forming apparatus according to any one of claims 1 to 8, wherein the pressure of the image forming apparatus is increased. Further, it has an image quality detecting unit for detecting the image quality of the image transferred by the transfer unit or the image quality of the residual image remaining on the intermediate transfer body after the transfer unit is transferred.
The precoat layer forming portion changes the thickness of the precoat layer according to the image quality detected by the image quality detecting unit.
The image forming apparatus according to any one of claims 1 to 6. The image quality detection unit detects the transfer rate of the transferred image transferred by the transfer unit or the transfer rate of the residual image remaining on the intermediate transfer body.
The precoat layer forming portion changes the thickness of the precoat layer according to the transfer rate of the transferred image detected by the image quality detection unit or the transfer rate of the residual image.
The image forming apparatus according to claim 10. The image forming apparatus according to claim 11, wherein the precoat layer forming portion increases the thickness of the precoat layer when the transfer rate of the transferred image or the transfer rate of the residual image is less than the first predetermined value. .. The transfer unit records the ink when the transfer rate of the transferred image or the transfer rate of the residual image detected by the image quality detection unit is equal to or higher than the first predetermined value and less than the second predetermined value. The image forming apparatus according to claim 12, wherein the pressure when transferring to a medium is increased. The image forming apparatus according to any one of claims 1 to 13, wherein the precoat layer forming unit changes the thickness of the precoat layer according to the type of recording medium input or selected by the user. The image forming apparatus according to any one of claims 1 to 13, wherein the precoat layer forming portion changes the thickness of the precoat layer when a user gives an instruction to change the transfer rate. The image forming apparatus according to any one of claims 1 to 15, wherein the ink applying portion applies the ink onto the precoat layer.

Images