JP5407879B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system.

  In an image forming apparatus using an electrophotographic system, in order to obtain optimum fixing conditions for each recording medium, the fixing temperature, the fixing nip width, and the like are determined according to information on the heat capacity (thickness, size, paper quality) of the recording medium. A fixing condition such as a fixing pressure and a fixing speed is changed (for example, see Patent Document 1).

  Also, there is a configuration in which fixing conditions are changed in consideration of information on ambient temperature and humidity in addition to information on a recording medium (see, for example, Patent Document 2).

  In addition, in order to prevent a change in color tone that occurs when the fixing condition is changed based on information on the recording medium, the condition for color tone correction is changed by a RIP (Raster Image Processor) device in conjunction with the change in the fixing condition. There is also a conventional example (see, for example, Patent Document 3).

  On the other hand, in recent years, electrophotographic color image forming apparatuses have entered the production market where offset printing machines have been mainstream, taking advantage of the features of small lots and variable printing. In the production market, in order to increase the irrelevant value of printed matter, the printed matter output from the image forming device can be further processed with a PP coating, press coating, varnish coating, etc. for the purpose of glossiness and surface protection. Has begun to seek.

  Among these, PP sticking has the problem of recycling because it sticks polypropylene to the surface of the printed matter (recycling paper takes time and effort to peel off vinyl and cannot be turned into used paper), and there is a problem of harmful gases during incineration. In the future, the press coat that is shrinking and applying a water-based resin varnish to the paper, then melting it with a large cylinder heated by steam and solidifying it to a mirror finish is a specialized processing company. Because it is necessary to carry and process, there is a problem that it does not match the industry flow where a short delivery time is required and the cost is high.

  At present, surface processing with a varnish coater that coats and dries the surface of the printed material, which can be in-line connected directly to the latter stage of the image forming apparatus, is a low-cost process. It is regarded as a promising post-processing means. Patent Documents 4 to 6 disclose techniques related to a varnish coater.

  However, when a printed matter output by an image forming apparatus using an electrophotographic method is post-processed by a varnish coater, a problem that the toner is peeled off from the recording medium occurs or the glossiness changes, so that the color gamut is reduced. It may change, and the malfunction that a desired color cannot be obtained may occur.

In the conventional example, the fixing condition or the color tone correction condition of the RIP device is changed according to the recording medium and the surrounding environment so that the best result can be obtained as an output product of an electrophotographic image forming apparatus. However, on the premise that the output product of the image forming apparatus is post-processed by a varnish coater, there are no cases where the fixing condition or the color tone correction condition of the RIP apparatus is optimized.
Further, the above-mentioned literature relating to the varnish coater is not a thing that takes into consideration the fixing conditions.
For this reason, in the conventional publicly known technology, it has been impossible to prevent problems that may occur when the printed matter output by the above-described image forming apparatus is post-processed by a varnish coater.

  The present invention has been made in view of the above problems in the prior art, and even when a printed matter output by an image forming apparatus using an electrophotographic system is post-processed by a varnish coater, the toner is peeled off from the recording medium. It is an object of the present invention to provide an image forming apparatus capable of obtaining a printed matter that does not have a problem.

The present invention provided to solve the above problems is as follows.
[1] Based on raster image data for each predetermined color, an image forming unit (toner image forming unit) that superimposes a plurality of color toner images on a recording medium (recording paper P) to form an unfixed toner image for color 2M, 2C, 2Y, 2K, primary transfer unit 3, secondary transfer unit 5), a fixing unit (fixing device 6) for fixing an unfixed toner image on the recording medium, and the recording medium as post-processing Information input means (operation panel 9 or a control unit of the image forming apparatus) for inputting information on whether or not to perform varnishing on the toner image fixing surface, and correcting the color intensity of the input image data for each predetermined color. Color intensity correction means (RIP device 7) for creating raster image data for each predetermined color, and when the information that the varnishing is performed is input to the information input means (Y in step S12) ), Nisco Than when not carried out over bets, the direction of increasing the thermal energy applied to the unfixed toner image on the recording medium by adjusting the fixing condition in the fixing unit (step S14), and the color intensity correction means, said When information indicating that the varnishing is performed is input to the information input unit, the condition for correcting the color intensity of the input image data for each predetermined color is changed, and the predetermined color is compared to when the varnishing is not performed. An image forming apparatus (FIGS. 1, 4 and 5) characterized in that correction is performed in a direction to decrease the dot gain of each halftone .
[2] The image according to [1], wherein the adjustment of the fixing condition in the fixing unit is to change at least one of a fixing temperature, a fixing nip width, a nip pressure, and a recording medium conveyance speed. Forming equipment.
[3] The image forming apparatus according to [1] or [2], further including a fixing condition setting unit (fixing condition setting unit 8) capable of arbitrarily setting an adjustment amount of the fixing condition in the fixing unit. .
[4] Information on the type of varnish used for post-processing is input to the information input means, and when the information indicating that the varnishing is performed is input to the information input means, the color intensity correction means The image according to any one of [1] to [3], wherein the condition for correcting the color intensity of the input image data for each predetermined color is changed in accordance with the type of varnish used for processing. Forming equipment.
[5] above, wherein the having a color intensity correction condition setting means capable of arbitrarily setting the condition for correcting the color intensity of the input image data for each of the predetermined color to the color intensity correcting means performs (1) to [4] The image forming apparatus according to any one of [4] .

  According to the image forming apparatus of the present invention, when varnishing is to be performed on a printed matter on which an image is formed based on input image data, an unfixed toner image on a recording medium is more than in normal printing without varnishing in advance. In the direction where the thermal energy applied to the toner increases, the fixing conditions are adjusted, and printing is performed with the toner melting degree higher than that during normal printing, so the printed matter output from the image forming apparatus is post-processed with a varnish coater. In addition, it is possible to prevent a problem that the toner is peeled off from the recording medium.

1 is a schematic cross-sectional view showing a main configuration of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view illustrating a configuration example of a fixing device used in the image forming apparatus in FIG. 1. 2 is a flowchart showing a standard image forming procedure performed in the image forming apparatus of FIG. 1. 2 is a flowchart illustrating an image forming procedure based on a varnish coat performed in the image forming apparatus of FIG. 1. It is an example of a setting table for adjusting fixing conditions performed by fixing condition setting means. It is an example of a conversion curve for the RIP device to correct the color intensity of an input value of image data to create raster image data. It is a figure which shows the relationship between the input value of image data, and the reflection density of the formed image.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic color laser printer (hereinafter simply referred to as a printer) will be described.
First, a basic configuration of the printer according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a main part of the printer according to the present embodiment. In this printer 1, toner image forming portions (also referred to as image forming portions) 2M, 2C, 2Y, and 2K of magenta, cyan, yellow, and black (hereinafter referred to as M, C, Y, and K) are formed. M, C, Y, and K toner images are transferred onto the intermediate transfer belt 4 in the primary transfer portion 3 for each color. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 4. The four-color toner image on the intermediate transfer belt 4 is secondarily transferred onto the recording paper (also referred to as recording medium or paper) P at the secondary transfer portion 5 at once. The recording paper P on which a full-color image is formed is discharged from the secondary transfer unit 5 and then sent to the fixing device 6 to fix the full-color image.

  In the present embodiment, a printer driver, a dedicated application, or the like is obtained from the operation panel 9 attached to the image forming apparatus or the information terminal device 10 such as a PC, scanner, or other terminal connected via a LAN. The thickness (basis weight) of the recording paper P, the type (information such as uncoated and coated paper or the brand of the paper), information on whether or not to perform post-processing with a varnish coater, and the type of varnish coater used for post-processing This information can be input to the RIP device 7 and the fixing condition setting means 8 in the image forming apparatus. The fixing condition setting means 8 determines the fixing temperature and fixing nip width (also referred to as nip width. In addition, the fixing speed and fixing pressure can be varied) based on the input information. change. In addition, the RIP device 7 adjusts the image processing (raster image to be created) for each color of M, C, Y, and K based on the input information.

Here, the configuration of the fixing device 6 will be described.
FIG. 2 is a cross-sectional view showing a configuration example of a fixing roller type fixing device used in the present invention.
The fixing device 6 includes a cylindrical fixing roller 62 and a pressure roller 64 that directly presses the fixing roller 62 in a rotatable manner to form a nip portion N. In addition, a separation member 65, which is a plate-like member having a pointed tip that prevents the recording paper from being wound around the fixing roller 62, is provided in the vicinity of the fixing roller 62 at the nip N exit.

  Here, the fixing roller 62 is a roller in which a heat-resistant elastic layer such as silicone rubber (solid silicone rubber) or silicone sponge (foamed silicone rubber) is formed on the outer periphery of a hollow cylindrical base roller. The fixing roller 62 has a heater 62h, and lighting control of the heater 62h is performed so that the fixing can be properly performed at the nip portion N based on the surface temperature of the fixing roller 62 detected by the temperature detection sensor 62s. Is called.

  As shown in FIG. 2, the pressure roller 64 is provided with a pressure means including a pressure lever 66, a spring 67, a pressure intermediate member 66 a, and a cam 68. The pressure roller 64 is pressed against the fixing roller 62 by the pressure means to form a nip portion N or to open the nip portion N. Further, the fixing nip width of the nip portion N can be changed to a plurality of sheet passing states.

  As an operation of bringing the pressure roller 64 into a pressure state by the pressure means, first, when the cam 68 is rotated by a constant rotation angle in the direction of the arrow in FIG. The pressurizing intermediate member 66a is pushed up (in the direction of the arrow in FIG. 2). When the pressing intermediate member 66a is pushed to the position of the pressing intermediate member 66a ', the spring 67 fixed to the pressing intermediate member 66a pushes up the end of the pressing lever 66 with a constant pressure. Next, when the end of the pressure lever 66 on the spring 67 side is pushed up, the pressure lever 66 rotates about the support shaft 66b (counterclockwise direction in FIG. 2). Next, the pressure portion 66 c located between the end of the pressure lever 66 on the spring 67 side and the support shaft 66 b abuts against the shaft of the pressure roller 64 and acts to push in the direction of the fixing roller 62. Finally, the pressure roller 64 is pushed up to the position of the pressure roller 64 ′ and presses against the fixing roller 62 with a constant pressure to form the nip portion N. Note that the spring 67 can be omitted as the pressurizing means. In this case, the cam 68 acts to push up the end of the pressurizing lever 66 directly.

  At this time, the pressure roller 64 bites into the fixing roller 62 at a predetermined depth (for example, 2 to 4 mm). As a result, the nip portion N has a predetermined fixing nip width.

  In the fixing device 6, the pressure state of the pressure roller 64 is changed by the pressure means to change the contact state with the fixing roller 62, and the thickness, type (paper type) of the recording paper P, etc. It is possible to switch the fixing nip width of the nip portion N in a plurality of stages correspondingly.

  When driving the fixing device 6, for example, in FIG. 2, the pressure roller 64 is driven to rotate counterclockwise in the drawing by a drive motor provided for the fixing device 6. Further, the fixing roller 62 rotates in the direction in which the recording paper P is discharged (clockwise in FIG. 2). Further, at the time of fixing, the fixing roller 62 is heated until the temperature detected by the temperature detection sensor 62 s reaches a predetermined temperature (for example, a temperature suitable for toner fixing) by the heat generated by the heater 62 h disposed inside. . If necessary, the pressure roller 64 is also heated until the temperature detected by the temperature detection sensor 64s reaches a predetermined temperature due to the heat generated by the heater 64h disposed therein.

  Next, the recording paper P on which the unfixed toner is formed is passed through the nip portion N (paper passing from the right side to the left side in the drawing), and the unfixed toner is applied to the recording paper P by pressurization and heating in the nip portion N. Fixing is performed by heat fusing.

FIG. 3 shows a standard image forming procedure performed by the printer 1.
(S1) First, image data is input from the information terminal device 10 to the printer 1. At the same time, information (thickness (basis weight), type (information such as non-coated and coated paper or brand of paper)) and printing conditions (print size, number of sheets, etc.) regarding the recording paper P are input.
(S2) The RIP device 7 performs necessary image processing 1 on the input image data. That is, the input image data is converted into a color signal corresponding to four-color toner, and other necessary corrections are performed on the color signal, and raster image data corresponding to each four-color toner is output.
(S3) The fixing condition setting means 8 determines the fixing condition 1 (fixing temperature, fixing nip width, nip pressure, recording paper conveyance speed) in the fixing device 6 based on the input information (information about the recording paper P, printing conditions). Etc.).
(S4) The toner image forming units 2M, 2C, 2Y, and 2K perform image formation based on the raster image data output from the RIP device 7. Specifically, each of the toner image forming units 2M, 2C, 2Y, and 2K includes a rotating photosensitive drum, and a charger, an exposure device, a developing device, and a transfer device (primary) arranged along the outer peripheral surface of the photosensitive drum. And a transfer unit 3). After a charge is uniformly applied to the surface of the photosensitive drum by the charger, the exposure device irradiates the surface of the photosensitive drum with laser light in accordance with the raster image data. Then, an electrostatic latent image is formed, and then developed by a developing device, so that a toner image is formed on the surface of the photosensitive drum.
(S5) Next, the M, C, Y, and K toner images formed by the toner image forming units 2M, 2C, 2Y, and 2K are transferred onto the intermediate transfer belt 4 in the primary transfer unit 3 for each color. As a result, a four-color toner image is formed, and the four-color toner image on the intermediate transfer belt 4 is secondarily transferred onto the recording paper P by the secondary transfer unit 5.
(S6) The fixing device 6 is driven under the fixing condition 1 set in step S3, and the four-color toner image on the recording paper P is fixed and formed as a full-color image on the recording paper P conveyed. The

  Here, in the present invention, a toner image fixed on the recording paper P by the image forming apparatus (printer 1) (printer 1) in FIG. 1 (printed material) is subjected to varnish coating on the toner image fixing surface of the recording paper P by a varnish coater as post-processing. It is assumed that there are two cases: a case and a case where varnish coating is not applied.

  The varnish coating is performed by, for example, a roll coating apparatus (referred to as a varnish coater). The image forming apparatus (printer 1) and the varnish coater shown in FIG. Varnishing may be performed after the formation (toner image transfer) process and the fixing process, or the image forming apparatus (printer 1) and the varnish coater shown in FIG. Also good.

  The types of varnish used in the varnish coater include UV varnish, oily varnish, and aqueous varnish. The varnish coater mainly has different drying means depending on the varnish used. The UV varnish mainly uses a UV (ultraviolet) lamp as a drying means, but may be used in combination with hot air drying. In general, oily varnish and aqueous varnish use both IR (infrared) lamp irradiation and hot air drying as drying means. Varnish is compatible with the toner components. If the compatibility between the toner used in the image forming apparatus and the varnish is poor, the varnish may not be uniformly applied to the surface of the printed material of the image forming apparatus. It is selected in consideration of compatibility.

  By the way, when the printed matter output by the image forming apparatus is post-processed by a varnish coater which is another processing device provided outside the image forming apparatus, heat is again applied to the printed matter by the varnish drying means in the varnish coater. Become. At this time, the toner on the recording paper is melted, and there is a case where the toner is peeled off from the recording paper.

The inventors examined the phenomenon and found that sufficient fixing strength was secured for the printed matter of the image forming apparatus, but the toner was peeled off from the recording paper during the post-processing with the varnish coater. It was. In addition, it has been found that this is likely to occur when the toner adhesion amount in the color overlap portion is large and when the melting degree of the toner is relatively low at the time of fixing in the image forming apparatus.
Based on these findings, the inventors have intensively studied to improve the defect and have made the present invention.

  That is, the image forming apparatus according to the present invention includes information input means for inputting information on whether or not to varnish the toner image fixing surface of the recording paper P as post-processing, and varnishes the information input means. When the information is input, the fixing condition in the fixing unit is adjusted in the direction in which the thermal energy applied to the unfixed toner image on the recording medium is increased as compared with the case where varnishing is not performed. Is.

  Here, the information input unit may be the operation panel 9 or a control unit of the image forming apparatus. That is, information on whether or not to varnish the toner image fixing surface of the recording paper P as post-processing from information input from the operation panel 9 or printing condition information sent together with image data from the information terminal device 10 get. Note that the varnish coater outside the image forming apparatus includes the configurations described in Patent Documents 4 to 6 described above.

The main configuration of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 4 is a flowchart for explaining an image forming procedure performed in the printer 1.
(S 11) First, image data is input from the information terminal device 10 to the printer 1. At the same time, information (thickness (basis weight), type (information such as non-coated and coated paper or paper brand)) and printing conditions (print size, number of sheets, etc.) relating to the recording paper P are input (print job).
(S12) Next, for this print job, it is confirmed whether or not varnish coating is performed on the toner image fixing surface of the recording paper P as post-processing. Note that when varnishing is performed, varnish type information input in advance is also set. This confirmation is performed based on information input from the operation panel 9 or print condition information sent from the information terminal device 10 together with image data.

When the varnish coat is present (Y in Step S12), a series of processing from Step S13 to S18 is performed.
(S13) The RIP device 7 performs necessary image processing 1 on the input image data. Here, it may be the same as the image processing in the standard image forming procedure described above. As a result, the input image data is converted into a color signal corresponding to four-color toner, and other necessary corrections are performed on the color signal, and raster image data corresponding to each four-color toner is output.
(S14) Next, the fixing condition setting means 8 is based on the input information (information relating to the recording paper P, printing conditions), rather than when varnishing is not performed (in the above-described standard image forming procedure). The fixing condition in the fixing device 6 is adjusted and set in a direction to increase the thermal energy applied to the unfixed toner image on the recording paper P (fixing condition 2).
(S15) The toner image forming units 2M, 2C, 2Y, and 2K perform image formation based on the raster image data output from the RIP device 7.
(S16) Next, the M, C, Y, and K toner images formed by the toner image forming units 2M, 2C, 2Y, and 2K are superimposed and transferred onto the intermediate transfer belt 4 in the primary transfer unit 3 of each color. As a result, a four-color toner image is formed, and the four-color toner image on the intermediate transfer belt 4 is secondarily transferred onto the recording paper P by the secondary transfer unit 5.
(S17) The fixing device 6 is driven under the fixing condition 2 set in step S14, and the four-color toner image on the recording paper P is fixed and formed as a full-color image on the recording paper P conveyed. The
(S18) Thereafter, the toner image fixing surface of the recording paper P is varnished with a varnish coater, and the process ends.

  Further, when there is no varnish coat (N in step S12), a series of processing from step S19 to S1d is performed. This is the same as steps S2 to S6 in FIG. 3, and details are omitted.

  Here, the adjustment of the fixing condition by the fixing condition setting means 8 performed in step S14 is preferably to change at least one of the fixing temperature, the fixing nip width, the nip pressure, and the conveyance speed of the recording paper P.

  FIG. 5 is a setting table for adjusting the fixing conditions performed by the fixing condition setting means 8. Here, the thickness (basis weight) of the recording paper P, the type (two coated papers (Coat 1, Coat 2), non-coated paper (non-coated)), and which type of varnish coater is used for post-processing. An example of a setting table for changing fixing conditions in accordance with information on whether or not to perform varnish coating and information on the type of varnish coater used for post-processing is shown. The setting table is set as appropriate.

  In FIG. 5, the column 15 indicates normal fixing conditions (fixing temperature, fixing nip width) when varnishing is not performed, and the column 16 is when varnishing is performed (varnish corrections a, b, c). ) For the normal fixing conditions. These fixing conditions and correction amounts are classified according to the weighing and type of paper (recording paper P).

  In the setting table example of FIG. 5, the fixing temperature and the fixing nip width are listed as the fixing conditions. The setting when performing varnish coating is such that the fixing temperature is higher than normal, and the fixing nip width is higher than normal. It is set to correct in a wider direction. The setting for increasing the fixing temperature and the setting for widening the fixing nip width mean adjustment in the direction of increasing the thermal energy applied to the unfixed toner image on the paper. When the nip pressure and recording paper transport speed parameters are entered in the setting table of FIG. 5, the nip pressure for varnishing is higher than normal, and the recording paper transport speed is slower than normal. Make corrections.

  The reason for changing the parameters of the fixing conditions in the direction of increasing the thermal energy applied to the toner on the paper when performing varnish coating is to increase the melting degree of the toner. Here, if the thermal energy applied to the toner on the paper is increased, the glossiness of the printed matter will be higher than the optimum glossiness that the image forming apparatus is aiming at, but the gloss will be further increased by post-processing varnish. Therefore, the increase in glossiness is not a problem here. However, if the thermal energy applied to the toner is excessively increased, hot offset may occur. Therefore, the change of the fixing condition is limited to the minimum necessary to prevent the toner from being peeled off by the varnish coater.

  In the setting table example of FIG. 5, three types of setting frames a, b, and c are provided as settings when performing varnishing. Since the amount of fixing conditions that can prevent toner peeling differs depending on the drying means of the varnish coater described above (secondary heat level applied to the printed matter by the varnish coater), toner peeling is prevented for each of them. The minimum necessary correction is possible. Note that the setting table for determining the correction amount is determined in advance through experiments or the like.

  By performing varnish coating, gloss can be imparted to the printed matter and the commercial value can be increased. When performing varnishing, the fixing condition setting unit 8 selects an optimal fixing condition from the setting table of FIG. 5 based on the input information (information about the recording paper P, printing conditions), and the fixing of the fixing device 6 is performed. Change the condition. By doing so, it is possible to prevent the occurrence of a problem that the toner is peeled off from the recording medium when post-processing with a varnish coater.

  Many types of varnish coaters are sold by many manufacturers, and are mainly used by printers, so they are often custom-made products. Accordingly, the table for determining the correction amount of the fixing condition is prepared with some conditions as a default, and some free boxes are prepared, and the operation panel 9 attached to the image forming apparatus is used. It is preferable to have a mechanism that allows the user to arbitrarily input conditions that are optimal for the conditions of the varnish coater used. That is, it is preferable that the fixing condition setting unit 8 can arbitrarily set the adjustment amount of the fixing condition in the fixing device 6. By doing so, it is possible to flexibly cope with the difference in the tendency of occurrence of defects due to the difference in the varnish drying means of the varnish coater.

Next, the operation of the RIP device 7 will be described.
The RIP device 7 corrects the input value (color intensity) of the image data of each color of M, C, Y, K using a predetermined conversion curve (FIG. 6) according to the characteristics of the image forming device (printer 1). And color intensity correction means for creating raster images of M, C, Y, and K colors. The toner image forming units 2M, 2C, 2Y, and 2K of the image forming apparatus create M, C, Y, and K toner images based on the corrected raster image output from the RIP device 7.

  In the present invention, when information indicating that varnishing is performed is input to the information input means (when varnishing is present (Y in step S12)), the RIP device 7 determines each color of M, C, Y, and K in step S13. It is preferable to change the conditions for correcting the color intensity of the input image data.

  For example, if the curve 30 in FIG. 6 is a conversion curve that is normally used (conversion curve when varnishing is not performed), in the present invention, in addition to the conversion curve 30, a conversion curve 31 when varnishing is performed If the varnish coat is provided separately (Y in Step S12), it is preferable that the conversion curve 31 is selected in Step S13. Furthermore, it is preferable that a conversion curve for varnish coat as indicated by reference numeral 31 is provided as a plurality of conversion tables 20 to 22 so as to correspond to the type of varnish coater. Although not shown in the example of FIG. 6, a plurality of such conversion curve sets may be provided corresponding to the type of recording paper.

  Here, in FIG. 7, when performing varnish coating, the fixing condition parameters are changed in the direction in which the thermal energy applied to the toner on the paper is increased by the image forming apparatus (step S14), and 2 is further processed by the post-processing varnish coater. An example of the tendency of the reflection density of the printed matter after the next heat is applied and the glossiness by the varnish coat is given is shown as a curve 41. In FIG. 7, a curve 40 is a reflection density curve with respect to an input value of image data under normal conditions (printed matter of a normal image forming apparatus, no varnish).

  When the curve of reference numeral 41 is compared with the curve of reference numeral 40, in the portion where the input value of the image data is 100% (solid image portion), the glossiness has increased due to the varnish, so the reflection density itself has increased. Yes. On the other hand, in a portion where the input value of image data is 50 to 80% (halftone portion), for example, the reflection density does not increase at the same ratio as the solid image portion, but the toner melting degree increases and the halftone is reduced. Since the area of the dots to be constructed increases (that is, the halftone dot gain increases), the reflection density of the halftone part tends to increase at a rate larger than the increase rate of the reflection density of the solid image part. . Therefore, when the information to be post-processed by the varnish coater is input, the color intensity of the input image data is corrected by the RIP device 7 in a direction to reduce the halftone dot gain compared to the normal printing (when varnish coating is not performed). It is preferable to do.

  Also, as in the case of adjusting the fixing conditions, in order to support various varnish coaters, in addition to preparing several conversion curves for varnish as a default, several free boxes are prepared and images It is preferable that a conversion curve that is optimal for the conditions of the varnish coater used by the user can be arbitrarily input from the operation panel 9 attached to the forming apparatus. That is, it is preferable to include color intensity correction condition setting means that can arbitrarily set conditions for correcting the color intensity of input image data of M, C, Y, and K colors performed by the RIP device 7. By doing so, it is possible to flexibly cope with the difference in the tendency of occurrence of defects due to the difference in the varnish drying means of the varnish coater.

  As described above, when performing varnishing, the RIP device 7 selects an optimal conversion curve based on input information (information on the recording paper P, printing conditions), and uses this to convert a raster image. Then, the image forming apparatus creates a toner image based on the corrected raster image. In this way, image processing is performed in anticipation of a change in glossiness in post-processing by the varnish coater, so that the recording is performed by the fixing device 6 in order to prevent the toner from peeling off from the recording paper P as described above. The parameters of the fixing conditions are changed in a direction to increase the thermal energy applied to the unfixed toner image on the paper P, and further, secondary heat is applied by a post-processing varnish coater and glossiness by the varnish is imparted. The increase in dot gain caused by this can be canceled in advance, and it is possible to prevent a problem that the color reproduction range changes after varnishing and a desired color cannot be obtained.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

1 Printer (image forming device)
2M, 2C, 2Y, 2K Toner image forming unit 3 Primary transfer unit 4 Intermediate transfer belt 5 Secondary transfer unit 6 Fixing device 7 RIP device 8 Fixing condition setting means 9 Operation panel 10 Information terminal device (PC or other terminal)
15 Normal fixing conditions 16 Correction amount for normal fixing conditions when performing varnishing 20-22 Conversion table of conversion curve of RIP device 30 Normal (without varnishing) conversion curve 31 Conversion curve when performing varnishing 40 Normal image Curve of reflection density with respect to input value of image data of printed material of forming apparatus 41 Curve of reflection density with respect to input value of image data of printed material after post-processing by varnish coater 62 Fixing roller 62h, 64h Heater 62s, 64s Temperature detection sensor 64, 64 'pressure roller 65 separation member 66 pressure lever 66a, 66a' pressure intermediate member 66b support shaft 66c pressure part 67 spring 68 cam P recording medium (recording paper)

Japanese Patent Laid-Open No. 08-036325 Japanese Patent No. 4098726 Japanese Patent No. 2687296 Japanese Patent Laid-Open No. 2001-191489 JP 2003-182031 A JP 2007-176044 A

Claims (5)

An image forming unit that forms an unfixed toner image for color by superimposing a plurality of color toner images on a recording medium based on raster image data for each predetermined color;
A fixing unit for fixing an unfixed toner image on the recording medium;
Information input means for inputting information as to whether or not to varnish the toner image fixing surface of the recording medium as post-processing;
Color intensity correction means for correcting the color intensity of the input image data for each predetermined color and creating raster image data for each predetermined color , and
When information indicating that the varnishing is performed is input to the information input unit, the heat energy applied to the unfixed toner image on the recording medium is increased in the fixing unit in comparison with the case where the varnishing is not performed. Adjust the fixing conditions ,
When the information indicating that the varnishing is performed is input to the information input unit, the color intensity correcting unit changes a condition for correcting the color intensity of the input image data for each predetermined color and does not perform the varnishing The image forming apparatus is characterized in that correction is performed in a direction to reduce the halftone dot gain for each predetermined color .   The image forming apparatus according to claim 1, wherein the adjustment of the fixing condition in the fixing unit is to change at least one of a fixing temperature, a fixing nip width, a nip pressure, and a recording medium conveyance speed.   The image forming apparatus according to claim 1, further comprising a fixing condition setting unit that can arbitrarily set an adjustment amount of the fixing condition in the fixing unit. In the information input means, information on the type of varnish used for post-processing is input,
When information indicating that the varnishing is performed is input to the information input unit, the color intensity correction unit corresponds to the type of varnish used for the post-processing, and the color intensity of the input image data for each predetermined color changing the condition for correcting the image forming apparatus according to any one of claims 1 to 3, wherein. Any one of claims 1 to 4, characterized by comprising a color intensity correction condition setting means capable of arbitrarily setting the condition for correcting the color intensity of the input image data for each of the predetermined color performed by the color intensity correcting means The image forming apparatus according to one item.

Images